diff --git a/Pmodules/libpbuild.bash b/Pmodules/libpbuild.bash
index bccf179..42dd0e6 100644
--- a/Pmodules/libpbuild.bash
+++ b/Pmodules/libpbuild.bash
@@ -23,7 +23,6 @@ declare -a CONFIGURE_ARGS=()
 declare -a PATCH_FILES=()
 declare -a PATCH_STRIPS=()
 declare -a PATCH_STRIP_DEFAULT='1'
-declare -a MODULE_DOCFILES=()
 declare -- configure_with='auto'
 
 #.............................................................................
@@ -425,6 +424,10 @@ pbuild.set_urls(){
 #	Maybe we should use a dictionary in the future.
 #
 pbuild::set_sha256sum() {
+	if [[ ${opt_yaml} == 'yes' ]]; then
+		std::info \
+			"Using ${FUNCNAME} is deprecated with YAML module configuration files."
+	fi
 	SOURCE_SHA256_SUMS+=("$1")
 }
 readonly -f pbuild::set_sha256sum
@@ -557,15 +560,25 @@ pbuild::prep() {
 				 "${module_name}/${module_version}:" \
 				 "source file '${_result}' is not readable!"
 
-		local sha256_sum=''
-		local hash=''
-		for hash in "${SOURCE_SHA256_SUMS[@]}"; do
-			if [[ ${hash} =~ $fname: ]]; then
-				sha256_sum="${hash#*:}"
+		local -- sha256_sum=''
+		if [[ "${opt_yaml}" == 'yes' ]]; then
+			if [[ -v SHASUMS[${fname}] ]]; then
+				sha256_sum="${SHASUMS[${fname}]}"
 			fi
-		done
+		else
+			local hash=''
+			for hash in "${SOURCE_SHA256_SUMS[@]}"; do
+				if [[ ${hash} =~ $fname: ]]; then
+					sha256_sum="${hash#*:}"
+					break
+				fi
+			done
+		fi
 		if [[ -n "${sha256_sum}" ]]; then
 			check_hash_sum "${dir}/${fname}" "${sha256_sum}"
+			std::info "${module_name}/${module_version}: SHA256 hash sum is OK ..." 
+		else
+			std::info "${module_name}/${module_version}: SHA256 hash sum missing NOK ..." 
 		fi
 	}
 
@@ -648,6 +661,11 @@ readonly -f pbuild::add_configure_args
 #..............................................................................
 #
 pbuild::use_autotools() {
+	if [[ ${opt_yaml} == 'yes' ]]; then
+		std::info \
+			"Using ${FUNCNAME} is deprecated with YAML module configuration files."
+	fi
+
 	configure_with='autotools'
 }
 readonly -f pbuild::use_autotools
@@ -655,6 +673,10 @@ readonly -f pbuild::use_autotools
 #..............................................................................
 #
 pbuild::use_cmake() {
+	if [[ ${opt_yaml} == 'yes' ]]; then
+		std::info \
+			"Using ${FUNCNAME} is deprecated with YAML module configuration files."
+	fi
 	configure_with='cmake'
 }
 readonly -f pbuild::use_cmake
@@ -689,6 +711,10 @@ readonly -f pbuild::use_cc
 declare -- compile_in_sourcetree='No'
 
 pbuild::compile_in_sourcetree() {
+	if [[ ${opt_yaml} == 'yes' ]]; then
+		std::info \
+			"Using ${FUNCNAME} is deprecated with YAML module configuration files."
+	fi
 	compile_in_sourcetree='Yes'
 }
 readonly -f pbuild::compile_in_sourcetree
@@ -791,6 +817,10 @@ pbuild::compile() {
 #   $@: documentation files relative to source
 #
 pbuild::install_docfiles() {
+	if [[ ${opt_yaml} == 'yes' ]]; then
+		std::info \
+			"Using ${FUNCNAME} is deprecated with YAML module configuration files."
+	fi
 	MODULE_DOCFILES+=("$@")
 }
 readonly -f pbuild::install_docfiles
@@ -862,8 +892,17 @@ pbuild.build_module_legacy(){
 }
 readonly -f pbuild.build_module_legacy
 
+declare -n Config
+declare -- Systems
 pbuild.build_module_yaml(){
-	_build_module "$@"
+	local -- module_name="$1"
+	local -- module_version="$2"
+	Config=$3
+	local -- module_relstage="${Config['relstage']}"
+	local -- tmp="${Config['systems']//::/, }"
+	Systems="${tmp:1:-1}"
+	shift 3
+	_build_module "${module_name}" "${module_version}" "${module_relstage}" "$@"
 }
 readonly -f pbuild.build_module_yaml
 
@@ -1145,13 +1184,17 @@ _build_module() {
 
 	#......................................................................
 	check_supported_systems() {
-		(( ${#SUPPORTED_SYSTEMS[@]} == 0 )) && return 0
-		for sys in "${SUPPORTED_SYSTEMS[@]}"; do
-			[[ ${sys,,} == ${system,,} ]] && return 0
-		done
-		std::die 1 \
-			 "%s " "${module_name}/${module_version}:" \
-			 "Not available for ${system}."
+		if [[ "${opt_yaml,,}" == 'no' ]]; then
+			(( ${#SUPPORTED_SYSTEMS[@]} == 0 )) && return 0
+			for sys in "${SUPPORTED_SYSTEMS[@]}"; do
+				[[ ${sys,,} == ${system,,} ]] && return 0
+			done
+			std::die 1 \
+				 "%s " "${module_name}/${module_version}:" \
+				 "Not available for ${system}."
+		else
+			: debug "Systems: $Systems"
+		fi
 	}
 
 	#......................................................................
@@ -1454,26 +1497,71 @@ _build_module() {
 	}
 
 	install_release_file() {
- 		local -r release_file="${modulefile_dir}/.release-${module_version}"
+ 		local -r legacy_config_file="${modulefile_dir}/.release-${module_version}"
+		local -- status_legay_config_file='unchanged'
+ 		local -r yaml_config_file="${modulefile_dir}/.config-${module_version}"
+		local -- status_yaml_config_file='unchanged'
 
-		if [[ -r "${release_file}" ]]; then
-			local release
-			read release < "${release_file}"
-			if [[ "${release}" != "${module_release}" ]]; then
+		if [[ -r "${legacy_config_file}" ]]; then
+			local relstage_legacy
+			read relstage_legacy < "${legacy_config_file}"
+			if [[ "${relstage_legacy}" != "${module_release}" ]]; then
+				status_legay_config_file='changed'
+			fi
+		else
+			status_legay_config_file='new'
+		fi
+		if [[ "${status_legay_config_file}" != 'unchanged' ]]; then
+			echo "${module_release}" > "${legacy_config_file}"
+		fi
+
+		if [[ -r "${yaml_config_file}" ]]; then
+			while read key value; do
+				local -n ref="${key:0:-1}"
+				ref="${value}"
+			done < "${yaml_config_file}"
+			if [[ "${relstage}" != "${module_release}" ]]; then
+				status_yaml_config_file='changed'
+			fi
+		else
+			status_yaml_config_file='new'
+		fi
+		if [[ "${status_yaml_config_file}" != 'unchanged' ]]; then
+			echo "relstage: ${module_release}" > "${yaml_config_file}"
+			echo "Systems: [${Systems}]" >> "${yaml_config_file}"
+		fi
+
+		case ${status_yaml_config_file},${status_legay_config_file} in
+			unchanged,unchanged | new,unchanged)
+				:
+				;;
+			unchanged,changed )
 				std::info \
 					"%s " \
 					"${module_name}/${module_version}:" \
-					"changing release from" \
-					"'${release}' to '${module_release}' ..."
-				echo "${module_release}" > "${release_file}"
-			fi
-		else
-			std::info \
-				"%s " \
-				"${module_name}/${module_version}:" \
-				"setting release to '${module_release}' ..."
-			echo "${module_release}" > "${release_file}"
-		fi
+					"changing release stage from" \
+					"'${relstage_legacy}' to '${module_release}' in legacy config file ..."
+				;;
+			unchanged,new )
+				std::info \
+					"%s " \
+					"${module_name}/${module_version}:" \
+					"setting release stage to '${module_release}' in legacy config file ..."
+				;;
+			changed,unchanged | changed,changed | changed,new | new,changed )
+				std::info \
+					"%s " \
+					"${module_name}/${module_version}:" \
+					"changing release stage from" \
+					"'${relstage_legacy}' to '${module_release}' ..."
+				;;
+			new,new )
+				std::info \
+					"%s " \
+					"${module_name}/${module_version}:" \
+					"setting release stage to '${module_release}' ..."
+				;;
+		esac
 	}
 
 	cleanup_build() {
@@ -1621,6 +1709,14 @@ _build_module() {
 				"removing release file '${release_file}' ..."
 			[[ "${dry_run}" == 'no' ]] && ${rm} -vf "${release_file}"
 		fi
+		release_file="${modulefile_dir}/.config-${module_version}"
+		if [[ -e "${release_file}" ]]; then
+			std::info \
+				"%s " \
+				"${module_name}/${module_version}:" \
+				"removing release file '${release_file}' ..."
+			[[ "${dry_run}" == 'no' ]] && ${rm} -vf "${release_file}"
+		fi
 		${rmdir} -p "${modulefile_dir}" 2>/dev/null || :
 	}
 
@@ -1679,7 +1775,7 @@ _build_module() {
 		"${module_name}/${module_version}:" \
 		${with_modules:+build with ${with_modules[@]}}
 
-	if [[ "${module_release}" == 'removed' ]]; then
+	if [[ "${module_release}" == 'remove' ]]; then
 		remove_module
 	elif [[ "${module_release}" == 'deprecated' ]]; then
 		deprecate_module
diff --git a/Pmodules/libstd.bash b/Pmodules/libstd.bash
index e9eda18..dbb3a3f 100644
--- a/Pmodules/libstd.bash
+++ b/Pmodules/libstd.bash
@@ -284,7 +284,7 @@ std::get_os_release() {
 }
 
 std::get_type() {
-	local -a signature=$(typeset -p "$1")
+	local -a signature=( $(typeset -p "$1") )
 	case ${signature[1]} in
 		-Ai* )
 			echo 'int dict'
diff --git a/Pmodules/modbuild.in b/Pmodules/modbuild.in
index e9c27f7..0baf4be 100755
--- a/Pmodules/modbuild.in
+++ b/Pmodules/modbuild.in
@@ -7,6 +7,8 @@
 #
 #.............................................................................
 
+echo "$0 $@"
+
 declare VERSION='@PMODULES_VERSION@'
 
 # get absolute path of script
@@ -70,7 +72,7 @@ USAGE:
 MANDATORY ARGUMENTS:
 
 version
-        Variant of module to build.
+        Version of module to build.
 
 SELECT VARIANT TO BUILD:
 
@@ -180,14 +182,32 @@ declare         opt_verbose='no'
 declare -a      opt_with_modules=()	# :FIXME: legacy build should also use the dict
 declare -A	opt_with_dict=()
 declare --	opt_config_file=''
+declare --	opt_debug='no'
 declare --      opt_yaml='yes'
 declare --	opt_variant=''
 
-declare		BUILD_SCRIPT=''
+declare --	BUILD_SCRIPT=''
 declare --      yaml_config_file=''
 declare -a      legacy_config_files=()
+declare --	module_name=''
 
 parse_args() {
+	#
+	# The first argument ($1) is the build-script, if called in the
+	# usual way:
+	#     ./<build-script> <version> [options]
+	# If called via:
+	#     modbuild <build-script> [options]
+	# the build-script MUST be passed as first argument.
+	#
+	BUILD_SCRIPT=$(std::get_abspath "$1")
+	test -r ${BUILD_SCRIPT} || \
+		std::die 1 "%s " \
+			 "Build script does not exist" \
+			 "or is not readable -- '$_'"
+	BUILDBLOCK_DIR=$(dirname "${BUILD_SCRIPT}")
+	shift 1
+
 	while (( $# > 0 )); do
 		case $1 in
 		-j )
@@ -200,9 +220,10 @@ parse_args() {
 		-v | --verbose )
 			trap 'echo "$BASH_COMMAND"' DEBUG
                         opt_verbose='yes'
+			set -x
 			;;
 		--debug )
-			set -x
+			opt_debug='yes'
 			;;
 		-f | --force-rebuild )
                         opt_force_rebuild='yes'
@@ -314,46 +335,25 @@ parse_args() {
 				shift
 			fi
 			;;
-                -- )
+                -- | '' )
                         :
                         ;;
 		-* )
 			std::die 1 "Invalid option -- '$1'"
 			;;
-		[=0-9]* | '.*' )
-			versions+=( "$1" )
-			;;
-		'')	
-			:
-			;;
 		* )
-			[[ -z "${BUILD_SCRIPT}" ]] || \
-				std::die 1 "%s "\
-					 "Build script already set to" \
-					 "'${BUILD_SCRIPT}' -- '$1'"
-		        BUILD_SCRIPT=$(std::get_abspath "$1")
-			test -r ${BUILD_SCRIPT} || \
-				std::die 1 "%s " \
-					 "Build script does not exist" \
-					 "or is not readable -- '$_'"
+			local -- arg="$1"
+			if [[ "${arg}" == */* ]]; then
+				module_name="${arg%/*}"
+				versions+=( {arg#*/} )
+			else
+				versions+=( "$1" )
+			fi
 			;;
 		esac
 		shift
 	done
 
-	# BUILD_SCRIPT is not set if called with `modbuild <version> [options]`
-	if [[ -z ${BUILD_SCRIPT} ]]; then
-		if [[ -r "${PWD}/build" ]]; then
-			if grep -q '#!.* modbuild' "${PWD}/build"; then
-				BUILD_SCRIPT="${PWD}/build"
-			fi
-		fi
-		if [[ -z ${BUILD_SCRIPT} ]]; then
-			std::die 1 "Don't know what to build!"
-		fi
-	fi
-	BUILDBLOCK_DIR=$(dirname "${BUILD_SCRIPT}")
-
 	# if no version is specified on the cmd-line, build all versions
 	(( ${#versions[@]} > 0)) || versions+=( '.*' )
 
@@ -511,7 +511,7 @@ get_yaml_file_fmt(){
 	Get format version of configuration file. Print the version number
 	to stdout if it is valid.
 	"
-	${yq} -e '.' "$1" &>- || \
+	${yq} -e '.' "$1" &>/dev/null || \
 		std::die 3 "%s -- %s" \
 			 "Error in YAML config file, please check with linter" \
 			 "$1"
@@ -531,9 +531,9 @@ get_yaml_file_fmt(){
 
 read_yaml_config_file() {
 	: "
-  	Test whether the configuration file passed with $1 provides
-	configuration for the module passed with $2. If yes, the
-	configuration for this module is printed.
+  	Test whether the configuration file '$1' provides configurations
+	for the module '$2'. If yes, the YAML block with the configuration
+	is printed to stdout.
 	"
 	local -- file_name="$1"
 	local -- module_name="$2"
@@ -575,6 +575,9 @@ declare -x V_MINOR=''		# second number in version string (or empty)
 declare -x V_PATCHLVL=''	# third number in version string (or empty)
 declare -x V_RELEASE=''		# module release (or empty)
 
+declare -A SHASUMS=()
+declare -a MODULE_DOCFILES=()
+
 parse_version() {
 	local v="$1"
 	V="$1"
@@ -621,28 +624,34 @@ parse_version() {
 }
 
 declare -A Yaml_valid_keys_for_module=(
-	['defaults']=1
-	['shasums']=1
-	['versions']=1
+	['defaults']=1			# !!map
+	['shasums']=1			# !!map
+	['versions']=1			# !!int
 )
+
 declare -A Yaml_default_config=(
-	["build_requires"]=''
-	["compile_in_sourcetree"]='No'
-	["configure_with"]='auto'
-	["default_variant"]=''
-	["group"]='Tools'
-	["group_deps"]=''
-	["overlay"]='base'
-	["relstage"]='unstable'
-	["runtime_deps"]=''
-	["script"]='build'
-	["suffix"]=''
-	["systems"]=''
-	["urls"]=''
-	["variant"]=''
+	["build_requires"]=''		# !!seq of strings
+	["compile_in_sourcetree"]='No'  # !!str
+	["configure_with"]='auto'	# !!str
+	["default_variant"]=''          # !!str
+	["docfiles"]=''			# !!seq of strings
+	["group"]='Tools'		# !!str
+	["group_deps"]=''		# !!map
+	["overlay"]='base'		# !!str
+	["relstage"]='unstable'		# !!str
+	["runtime_deps"]=''		# !!seq of strings
+	["script"]='build'		# !!str
+	["suffix"]=''			# !!str
+	["systems"]=''			# !!seq of strings
+	["urls"]=''			# !!map
+	["variant"]=''			# !!str
 )
 
-
+declare -A Yaml_valid_vk_keys=(
+	['config']=1			# !!map
+	['variants']=1			# !!map
+)
+	
 
 build_modules_yaml_v1(){
 	: "
@@ -655,32 +664,35 @@ build_modules_yaml_v1(){
         local -a with_modules=( $* )
 
 	check_yaml_keys(){
-		local -n valid_keys="$1"
-		local -n used_keys="$2"
-		used_keys=()
+		local -n valid_yaml_keys="$1"
+		local -n used_yaml_keys="$2"
+		used_yaml_keys=()
 		local -- key=''
 		local -a keys=()
-		keys=( $(${yq} '.|keys().[]' <<<"${yaml_mod_config}" 2>/dev/null) )
-		echo "DEBUG: top-level keys: ${keys[@]}"
+		keys=( $(${yq} '.|keys().[]' 2>/dev/null) )
+		debug "top-level keys: ${keys[@]}"
 		for key in "${keys[@]}"; do
-			[[ -v valid_keys[${key}] ]] || \
+			[[ -v valid_yaml_keys[${key}] ]] || \
 				std::die 3 "Invalid key in YAML configuration file -- ${key}"
-			used_keys[${key}]=1
+			used_yaml_keys[${key}]=1
 		done
 	}
 
-	local -A used_yaml_keys=()
-	#check_yaml_keys Yaml_valid_keys_for_module used_yaml_keys <<<"${yaml_mod_config}"
-	local -a keys=( $(${yq} '.|keys().[]' <<<"${yaml_mod_config}" 2>/dev/null) )
-	local -- key=''
-	echo "DEBUG: top-level keys: ${keys[@]}"
-	for key in "${keys[@]}"; do
-		[[ -v Yaml_valid_keys_for_module[${key}] ]] || \
-			std::die 3 "Invalid key in YAML configuration file -- ${key}"
-		used_yaml_keys[${key}]=1
-	done
-	[[ -v used_yaml_keys['versions'] ]] || \
-		std::die 3 "No version(s) specified in YAML configuration file."
+	get_value(){
+		local -- yaml_input="$1"
+		local -n val="$2"
+		local -- key="$3"
+		local -- expected_type="$4"
+		
+		local -- type=''
+		type=$( ${yq} ".${key} | type" 2>/dev/null <<<"${yaml_input}")
+		if [[ "${type}" != "${expected_type}" ]]; then
+			std::die 3 "%s" \
+				 "Value of '${key}' must be of type '${expected_type:2}', but is '${type:2}'!"
+		fi
+		val=$( ${yq} -e ".${key}" \
+			       2>/dev/null <<<"${yaml_input}" ) || val=''
+	}
 
 	get_config(){
 		local -- yaml_input="$1"
@@ -700,23 +712,22 @@ build_modules_yaml_v1(){
 		local -a keys=()
 		keys=( $( ${yq} -e ".|keys().[]" <<<"${yaml_input}" 2>/dev/null )) || \
 			std::die 3 "Oops: retrieving keys from:\n${yaml_input}"
-		echo "DEBUG: config keys: ${keys[@]}"
+		debug "config keys: ${keys[@]}"
+		local -- type;
 		for key in "${keys[@]}"; do
-			[[ -v dfl[$key] ]] || \
+			[[ -v dfl[${key,,}] ]] || \
 				std::die 3 "%s -- %s\n%s" \
-					 "Ivalid key in configuration" \
+					 "Invalid key in configuration" \
 					 "${key}" "${yaml_input}"
 			case ${key} in
 				compile_in_sourcetree )
-					value=$( ${yq} -e ".${key}" \
-						       2>/dev/null <<<"${yaml_input}" ) || \
-						value=''
+					get_value "${yaml_input}" value "${key}" '!!bool'
 					case ${value,,} in
-						true | on | yes )
-							cfg[${key}]='Yes'
+						true )
+							cfg[${key,,}]='Yes'
 							;;
-						false | off | no )
-							cfg[${key}]='No'
+						false )
+							cfg[${key,,}]='No'
 							;;
 						* )
 							std::die 3 "%s '%s' -- %s" \
@@ -727,12 +738,10 @@ build_modules_yaml_v1(){
 					esac
 					;;
 				configure_with )
-					value=$( ${yq} ".${key}" \
-						       2>/dev/null <<<"${yaml_input}" ) || \
-						value=''
+					get_value "${yaml_input}" value "${key}" '!!str'
 					case ${value,,} in
 						auto | cmake | autotools )
-							cfg[${key}]="${value,,}"
+							cfg[${key,,}]="${value,,}"
 							;;
 						* )
 							std::die 3 "%s '%s' -- %s" \
@@ -742,32 +751,52 @@ build_modules_yaml_v1(){
 							;;
 					esac
 					;;
-				urls | group_deps )
-					value=$( ${yq} -e ".${key}" \
-						       2>/dev/null <<<"${yaml_input}" ) || \
-						value=''
-					cfg[${key}]="${value}"
+				relstage )
+					get_value "${yaml_input}" value "${key}" '!!str'
+					case ${value,,} in
+						unstable | stable | deprecated )
+							cfg[${key,,}]="${value,,}"
+							;;
+						remove | removed )
+							cfg[${key,,}]='remove'
+							;;
+						* )
+							std::die 3 "%s '%s' -- %s" \
+								 "Invalid value for" \
+								 'relstage' \
+								 "${value}"
+							;;
+					esac
 					;;
-				systems | variant )
-					value=$( ${yq} -e ".${key}.[]" \
-						       2>/dev/null <<<"${yaml_input}" ) || \
-						value=''
+				urls )
+					get_value "${yaml_input}" value "${key}" '!!seq'
+					cfg[${key,,}]="${value}"
+					;;
+				group_deps )
+					get_value "${yaml_input}" value "${key}" '!!map'
+					cfg[${key,,}]="${value}"
+					;;
+				systems )
+					get_value "${yaml_input}" value "${key}" '!!seq'
+					readarray -t tmp <<<"${value}"
+					cfg[${key,,}]="${tmp[@]}"
+					;;
+				variant )
+					get_value "${yaml_input}" value "${key}" '!!seq'
 					readarray -t tmp <<<"${value}" 
 					printf -v tmp2 ":%s:" "${tmp[@]}"
-					cfg[${key}]="${tmp2}"
+					cfg[${key,,}]="${tmp2}"
 					:
 					;;
-				runtime_deps | build_requires )
-					value=$( ${yq} -e ".${key}[]" \
-						       2>/dev/null <<<"${yaml_input}" ) || \
-						value=''
-					cfg[${key}]="${value}"
+				docfiles | runtime_deps | build_requires )
+					get_value "${yaml_input}" value "${key}" '!!seq'
+					cfg[${key,,}]="${value}"
 					;;
 				* )
 					value=$( ${yq} -e ".${key}" \
 						       2>/dev/null <<<"${yaml_input}" ) || \
 						value=''
-					cfg[${key}]="${value}"
+					cfg[${key,,}]="${value}"
 			esac
 		done
 	}
@@ -788,7 +817,7 @@ build_modules_yaml_v1(){
 			l=()
 			# loop over semicolon separated list of keys
 			for k in ${key//;/ }; do
-				# do curly brackets expansion {}
+				# brace expansion of key
 				local list=()
 				eval list=( $k )
 				if [[ ${list[@]} =~ ${version} ]]; then
@@ -798,7 +827,7 @@ build_modules_yaml_v1(){
 			done
 		done
 		(( ${#refvar[@]} == 0 )) && \
-			std::die 3 "No configuration for version -- $1"
+			std::die 3 "No configuration for version -- ${version}"
 		return 0
 	}
 
@@ -858,39 +887,21 @@ build_modules_yaml_v1(){
 		fi
 	}
 
-	get_runtime_deps(){
-		local config="$1"
-		local -n with_modules="$2"
-
-		with_modules=( $(${yq} -e '.runtime_deps.[]' <<<"${config}" 2>/dev/null) )
-	}
-
-	get_build_requires(){
-		local -- config="$1"
-		local -n with_modules="$2"
-
-		with_modules=( $(${yq} -e '.build_requires.[]' <<<"${config}" 2>/dev/null) )
-		with_modules=( "${with_modules[@]/#/b:}" )
-	}
-
 	build_modules_compiler(){
 		local -- module_name="$1"
 		local -- module_version="$2"
 		local -n module_cfg="$3"
-		shift 3
-		local -a module_deps=( "$@" )
-
 		local -a with_compiler=()
 		get_group_deps  "${module_cfg['group_deps']}" 'compiler' with_compiler
-		echo "${with_compiler[@]}"
+		debug "${with_compiler[@]}"
 		
 		local compiler=''
 		for compiler in "${with_compiler[@]}"; do
 			pbuild.build_module_yaml \
 				"${module_name}" "${module_version}" \
-				"${module_cfg['relstage']}" \
+				"$3" \
 				"${compiler}" \
-				"${module_deps[@]}"
+				"${@:4}"
 		done
 	}
 
@@ -898,28 +909,25 @@ build_modules_yaml_v1(){
 		local -- module_name="$1"
 		local -- module_version="$2"
 		local -n module_cfg="$3"
-		shift 3
-		local -a module_deps=( "$@" )
-
 		local -a with_compiler=()
 		local -a with_hdf5=()
 		get_group_deps  "${module_cfg['group_deps']}" 'compiler' with_compiler
 		get_group_deps  "${module_cfg['group_deps']}" 'hdf5_serial' with_hdf5
-		echo "${with_compiler[@]}"
-		echo "${with_hdf5[@]}"
+		debug "${with_compiler[@]}"
+		debug "${with_hdf5[@]}"
 		local -- compiler
 		local -- hdf5
 		for compiler in "${with_compiler[@]}"; do
 			for hdf5 in "${with_hdf5[@]}"; do
-				echo "build $module_name/$module_version with $compiler and $hdf5"
-				echo "  runtime deps: ${runtime_deps[@]}"
-				echo "  build requires: ${build_requires[@]}"
+				debug "build $module_name/$module_version with $compiler and $hdf5"
+				debug "  runtime deps: ${runtime_deps[@]}"
+				debug "  build requires: ${build_requires[@]}"
 				pbuild.build_module_yaml \
 					"${module_name}" "${module_version}" \
-					"${module_cfg['relstage']}" \
+					"$3" \
 					"${compiler}" \
 					"${hdf5}" \
-					"${module_deps[@]}"
+					"${@:4}"
 			done
 		done
 	}
@@ -929,30 +937,27 @@ build_modules_yaml_v1(){
 		local -- module_name="$1"
 		local -- module_version="$2"
 		local -n module_cfg="$3"
-		shift 3
-		local -a module_deps=( "$@" )
-
 		local -a with_compiler=()
 		local -a with_mpi=()
 		get_group_deps  "${module_cfg['group_deps']}" 'compiler' with_compiler
 		get_group_deps  "${module_cfg['group_deps']}" 'mpi' with_mpi
 
-		echo "${with_compiler[@]}"
-		echo "${with_mpi[@]}"
+		debug "${with_compiler[@]}"
+		debug "${with_mpi[@]}"
 
 		local -- compiler
 		local -- mpi
 		for compiler in "${with_compiler[@]}"; do
 			for mpi in "${with_mpi[@]}"; do
-				echo "build $module_name/$module_version with $compiler and $mpi"
-				echo "  runtime deps: ${runtime_deps[@]}"
-				echo "  build requires: ${build_requires[@]}"
+				debug "build $module_name/$module_version with $compiler and $mpi"
+				debug "  runtime deps: ${runtime_deps[@]}"
+				debug "  build requires: ${build_requires[@]}"
 				pbuild.build_module_yaml \
 					"${module_name}" "${module_version}" \
-					"${module_cfg['relstage']}" \
+					"$3" \
 					"${compiler}" \
 					"${mpi}" \
-					"${module_deps[@]}"
+					"${@:4}"
 			done
 		done
 	}
@@ -961,9 +966,6 @@ build_modules_yaml_v1(){
 		local -- module_name="$1"
 		local -- module_version="$2"
 		local -n module_cfg="$3"
-		shift 3
-		local -a module_deps=( "$@" )
-
 		local -a with_compiler=()
 		local -a with_mpi=()
 		local -a with_hdf5=()
@@ -971,9 +973,9 @@ build_modules_yaml_v1(){
 		get_group_deps  "${module_cfg['group_deps']}" 'mpi' with_mpi
 		get_group_deps  "${module_cfg['group_deps']}" 'hdf5' with_hdf5
 
-		echo "${with_compiler[@]}"
-		echo "${with_mpi[@]}"
-		echo "${with_hdf5[@]}"
+		debug "${with_compiler[@]}"
+		debug "${with_mpi[@]}"
+		debug "${with_hdf5[@]}"
 
 		local -- compiler
 		local -- mpi
@@ -981,16 +983,16 @@ build_modules_yaml_v1(){
 		for compiler in "${with_compiler[@]}"; do
 			for mpi in "${with_mpi[@]}"; do
 				for hdf5 in "${with_hdf5[@]}"; do
-					echo "build $module_name/$module_version with $compiler, $mpi and $hdf5"
-					echo "  runtime deps: ${runtime_deps[@]}"
-					echo "  build requires: ${build_requires[@]}"
+					debug "build $module_name/$module_version with $compiler, $mpi and $hdf5"
+					debug "  runtime deps: ${runtime_deps[@]}"
+					debug "  build requires: ${build_requires[@]}"
 					pbuild.build_module_yaml \
 						"${module_name}" "${module_version}" \
-						"${module_cfg['relstage']}" \
+						"$3" \
 						"${compiler}" \
 						"${mpi}" \
 						"${hdf5}" \
-						"${module_deps[@]}"
+						"${@:4}"
 				done
 			done
 		done
@@ -1001,12 +1003,10 @@ build_modules_yaml_v1(){
 		local -- module_name="$1"
 		local -- module_version="$2"
 		local -n module_cfg="$3"
-		shift 3
-		local -a module_deps=( "$@" )
 		pbuild.build_module_yaml \
                         "${module_name}" "${module_version}" \
-                        "${module_cfg['relstage']}" \
-			"${module_deps[@]}"
+                        "$3" \
+			"${@:4}"
 	}
 
 	set_urls() {
@@ -1047,6 +1047,24 @@ build_modules_yaml_v1(){
 		local -- module_name="$1"
 		local -- module_version="$2"
 		local -n module_config="$3"
+
+		check_system(){
+			[[ -z ${module_config['systems']} ]] && return 0
+
+			set -o noglob
+			local -a systems=( ${module_config['systems']} )
+			set +o noglob
+
+			local -- system
+			for system in "${systems[@]}"; do
+				[[ "${opt_system}" == ${system} ]] && return 0
+				[[ "${HOSTNAME}" == ${system} ]] && return 0
+			done
+			std::info "Skipping variant '${module_version}', neither OS nor hostname match:"
+			std::info  " This system: ${opt_system}; hostname: ${HOSTNAME}"
+			std::info  " Systems to build on: ${systems[@]}"
+			return 1
+		}
 		
 		P="${module_name}"
 		parse_version "${module_version}"
@@ -1055,18 +1073,14 @@ build_modules_yaml_v1(){
 
 		# build this variant?
 		if [[ ":${module_config['variant']}:" != *:${build_variant}:* ]]; then
-			echo "DEBUG: don't build this variant: ${module_config['variant']} !=  *:${build_variant}:*"
+			debug "don't build this variant: ${module_config['variant']} !=  *:${build_variant}:*"
 			return 0
 		fi
 		
 		# build for this system?
-		if [[ -n ${module_config['systems']} ]] && \
-			   [[ ":${module_config['systems']}:" != *:${opt_system}:* ]]; then
-			echo "DEBUG: don't build for this system: ${module_config['systems']} !=  *:${opt_system}:*"
-			return 0
-		fi
+		check_system || return 0
 
-		echo "build variant ${module_name}/${module_version}"
+		debug "build variant ${module_name}/${module_version}"
 
 		local ol_name="${module_config['overlay']}"
 		[[ -v OverlayInfo[${ol_name}:inst_root] ]] || \
@@ -1086,14 +1100,19 @@ build_modules_yaml_v1(){
 		local -a runtime_deps=()
 		if [[ -n ${module_config['runtime_deps']} ]]; then
 			readarray -t runtime_deps <<<"${module_config['runtime_deps']}"
+			debug "runtime_deps=${runtime_deps[@]} length: ${#runtime_deps[@]}"
 		fi
-		echo "runtime_deps=${runtime_deps[@]} length: ${#runtime_deps[@]}"
+
 		local -a build_requires=()
 		if [[ -n ${module_config['build_requires']} ]]; then
 			readarray -t build_requires <<<"${module_config['build_requires']}"
+			build_requires=( "${build_requires[@]/#/b:}" )
+			debug "build_requires=${build_requires[@]} length: ${#build_requires[@]}"
+		fi
+
+		if [[ -n ${module_config['docfiles']} ]]; then
+			readarray -t MODULE_DOCFILES <<<"${module_config['docfiles']}"
 		fi
-		build_requires=( "${build_requires[@]/#/b:}" )
-		echo "build_requires=${build_requires[@]} length: ${#build_requires[@]}"
 
 		local -A build_functions=(
 			['Compiler']=build_modules_compiler
@@ -1131,42 +1150,47 @@ build_modules_yaml_v1(){
 			done
 		done
 	}
-	
+
+	local -A used_keys=()
 	local -- yaml_input=''
-	if [[ -v used_yaml_keys['defaults'] ]]; then
+	local -A default_config=()
+	local -- version_key=''
+	local -a version_keys=()
+	local -A shasums=()
+
+	check_yaml_keys Yaml_valid_keys_for_module used_keys <<<"${yaml_mod_config}"
+	[[ -v used_keys['versions'] ]] || \
+		std::die 3 "No version(s) specified in YAML configuration file."
+
+	if [[ -v used_keys['defaults'] ]]; then
 		yaml_input=$(${yq} '.defaults' <<<"${yaml_mod_config}" 2>/dev/null)
 	fi
-	local -A default_config=()
 	get_config "${yaml_input}" default_config Yaml_default_config
 
-	local -a version_keys
-	get_matching_version_keys version_keys "${version}" <<<"${yaml_mod_config}"
-
-	local -A valid_vk_yaml_keys=( ['config']=1 ['variants']=1 )
+	if [[ -v used_keys['shasums'] ]]; then
+		local yaml_input=$(${yq} '.shasums' <<<"${yaml_mod_config}" 2>/dev/null)
+		while read key value; do
+			SHASUMS[${key//:}]="${value}"
+		done <<<"${yaml_input}"
+	fi
 	
-	local -- version_key=''
+	
+	get_matching_version_keys version_keys "${version}" <<<"${yaml_mod_config}"
 	for version_key in "${version_keys[@]}"; do
 		local yaml_vk_config=$(get_yaml_vk_config "${version_key}" <<<"${yaml_mod_config}")
 
 		# check keys: allowed are 'config' and 'variants'
-		local -A used_vk_yaml_keys=()
-		#check_yaml_keys valid_vk_yaml_keys used_vk_yaml_keys <<<"${yaml_vk_config}"
-		local -a keys=( $(${yq} '.|keys().[]' <<<"${yaml_vk_config}" 2>/dev/null ) )
-		local -- key=''
-		echo "DEBUG: "vk keys: ${keys[@]}
-		for key in "${keys[@]}"; do
-			[[ -v valid_vk_yaml_keys[${key}] ]] || \
-				std::die 3 "Invalid key in YAML configuration file -- ${key}"
-			used_vk_yaml_keys[${key}]=1
-		done
+		used_keys=()
+		check_yaml_keys Yaml_valid_vk_keys used_keys <<<"${yaml_vk_config}"
 
 		# read config if set
 		local -A vk_config=()
 		yaml_input=''
-		if [[ -v used_vk_yaml_keys['config'] ]]; then
-			yaml_input=$(${yq} '.config.[]' <<<"${yaml_vk_config}" 2>/dev/null)
+		if [[ -v used_keys['config'] ]]; then
+			yaml_input=$(${yq} '.config' <<<"${yaml_vk_config}" 2>/dev/null)
+			debug "vk input: ${yaml_input}"
 		fi
-		echo "DEBUG: vk input: ${yaml_input}"
+		# reminder: if YAML input is empty, next line copies defaults to 'vk_config'
 		get_config "${yaml_input}" vk_config default_config
 
 		local -- yaml_variants=$(get_variants <<<"${yaml_vk_config}")
@@ -1175,7 +1199,7 @@ build_modules_yaml_v1(){
 		expand_version_key versions "${version_key}" "${version}"
 		local v=''
 		for v in "${versions[@]}"; do
-			echo "DEBUG: version: $v"
+			debug "version: $v"
 			if (( num_variants == 0 )); then
 				build_modules_variant \
 					"${name}" "${v}" \
@@ -1210,6 +1234,15 @@ build_modules() {
 
 parse_args "$@"
 
+if [[ "${opt_debug,,}" == 'no' ]]; then
+	debug(){
+		:
+	}
+else
+	debug(){
+		echo "DEBUG: " "$@"
+	}
+fi
 
 pbuild.jobs "${opt_jobs}"
 pbuild.force_rebuild "${opt_force_rebuild}"
@@ -1238,9 +1271,11 @@ export PMODULES_DISTFILESDIR PMODULES_TMPDIR
 declare -r BUILD_SCRIPT
 declare -r BUILDBLOCK_DIR
 
-# the module name is defined by the directory the build script is in
-IFS=/ read -r -a fname <<< "${BUILD_SCRIPT:1}"
-module_name=${fname[${#fname[@]}-2]}
+if [[ -z ${module_name} ]]; then
+	# the module name is defined by the directory the build script is in
+	IFS=/ read -r -a fname <<< "${BUILD_SCRIPT:1}"
+	module_name=${fname[${#fname[@]}-2]}
+fi
 
 for version in "${versions[@]}"; do
         build_modules "${module_name}" "${version}" "${opt_with_modules[@]}"
diff --git a/Pmodules/modulecmd.bash.in b/Pmodules/modulecmd.bash.in
index 0aeaf8a..04cac2a 100644
--- a/Pmodules/modulecmd.bash.in
+++ b/Pmodules/modulecmd.bash.in
@@ -187,7 +187,7 @@ die_illegal_group(){
                  "${CMD}" "${subcommand}" "invalid group name" "$1"
 }
 
-die_illegal_rel_stage(){
+die_illegal_relstage(){
         std::die 3 "%s %s: %s -- %s\n" \
                  "${CMD}" "${subcommand}" "invalid release stage" "$1"
 }
@@ -273,12 +273,6 @@ die_removing_collection_failed(){
 		 "cannot remove collection" "$1"
 }
 
-die_is_blocked(){
-	std::die 3 "%s %s: %s -- %s" \
-		 "${CMD}" "${subcommand}" \
-		 "module is blocked on this system" "$1"
-}
-
 get_module_config(){
 	: "
 	Read module configuration.
@@ -305,19 +299,21 @@ get_module_config(){
 	local -n ref_cfg="$1"
 	local -r dir="$2"
 	local -r modulefile="${dir}/$3"
+	debug "modulefile: $modulefile"
 
-	ref_cfg['rel_stage']='unstable'
+	ref_cfg['relstage']='unstable'
 	ref_cfg['systems']=''
 	ref_cfg['blocklist']=''
 	if [[ ! -v Dir2OverlayMap[${dir%/${PMODULES_MODULEFILES_DIR}*}] ]]; then
 		# this module is not in an overlay
-		ref_cfg['rel_stage']='stable'
+		ref_cfg['relstage']='stable'
 		return
 	fi
 	local -r config_file="${modulefile%/*}/.config-${modulefile##*/}"
-	local -r rel_stage_file="${modulefile%/*}/.release-${modulefile##*/}"
+	local -r relstage_file="${modulefile%/*}/.release-${modulefile##*/}"
 	if [[ -r ${config_file} ]]; then
-		local -- yaml=$(${yq} -e '.')
+		local -- yaml=$(${yq} -e '.' < "${config_file}")
+		debug "yaml: ${yaml}"
 		local -- key=''
 		for key in ${!ref_cfg[@]}; do
 			case "${key,,}" in
@@ -333,14 +329,14 @@ get_module_config(){
 					;;
 			esac
 			if [[ "${value}" != 'null' ]]; then
-				ref_cfg[${key}]="${value}"
+				ref_cfg[${key,,}]="${value}"
 			fi
 		done
 		return 0
-	elif [[ -r ${rel_stage_file} ]]; then
-		ref_cfg['rel_stage']=$( < "${rel_stage_file}" )
+	elif [[ -r ${relstage_file} ]]; then
+		ref_cfg['relstage']=$( < "${relstage_file}" )
 	else
-		ref_cfg['rel_stage']='unstable'
+		ref_cfg['relstage']='unstable'
 	fi
 }
 
@@ -352,17 +348,39 @@ is_available(){
 	- the blocklist is empty or the hostname is NOT in the list
 	"
 	local -n ref_cfg="$1"
-	local -- rel_stages="$2"
+	local -- relstages="$2"
 	local -- system="$3"
 	local -- hostname="$4"
 
-	[[ ":${rel_stages}:" =~ ":${ref_cfg['rel_stage']}:" ]] || return 1
-	if [[ "${ref_cfg['systems']}" != "" ]]; then
-		[[ "${ref_cfg['systems']//$'\n'/:}:" =~ "${system}" ]] || return 1
-	fi
-	if [[ "${ref_cfg['blocklist']}" != "" ]]; then
-		[[ "${ref_cfg['blocklist']//$'\n'/:}:" =~ "${hostname}" ]] && return 1
-	fi
+	check_relstage(){
+		[[ ":${relstages}:" =~ ":${ref_cfg['relstage']}:" ]]
+	}
+	check_blocklist(){
+		[[ -z ${ref_cfg['blocklist']} ]] && return 0
+		local -- s=''
+		for s in ${ref_cfg['blocklist']}; do
+			if [[ "${system}" == $s ]] || [[ "${HOSTNAME}" == $s ]]; then
+				return 0
+			fi
+		done
+		return 1
+	}
+	check_systems(){
+		[[ -z ${ref_cfg['systems']} ]] && return 0
+		local -- s=''
+		for s in ${ref_cfg['systems']}; do
+			if [[ "${system}" == $s ]] || [[ "${HOSTNAME}" == $s ]]; then
+				return 0
+			fi
+		done
+		return 1
+	}
+	set -o noglob
+	check_relstage && check_blocklist && check_systems
+	local -i ec=$?
+	set +o noglob
+	return ${ec}
+
 }
 
 #
@@ -557,7 +575,7 @@ USAGE:
 '
 
 subcommand_load() {
-	local rel_stage='undef'
+	local relstage='undef'
 	local current_modulefile=''
 	local prefix=''
 	local m=''
@@ -573,13 +591,13 @@ subcommand_load() {
 	#	none
 	get_load_hints() {
 		local -n output="$1"
-		local rel_stage=''
+		local relstage=''
 		output=''
 		while read -a line; do
                         [[ -z ${line} ]] && continue
-			rel_stage=${line[1]}
-			if [[ ! ":${UsedReleaseStages}:" =~ "${rel_stage}" ]]; then
-				output+="module use ${rel_stage}; "
+			relstage=${line[1]}
+			if [[ ! ":${UsedReleaseStages}:" =~ "${relstage}" ]]; then
+				output+="module use ${relstage}; "
 			fi
 			local group=${line[2]}
 	        	if [[ ! ":${UsedGroups}:" =~ ":${group}:" ]] && \
@@ -656,30 +674,6 @@ subcommand_load() {
 		g_env_must_be_saved='yes'
 	}
 
-	is_blocked() {
-		: "
-		test whether a module is blocked or not.
-
-		args:
-			$1: prefix of module
-
-		exit codes:
-			0: if blocked
-			1: otherwise
-		"
-		local _prefix="$1"
-		test -e "${_prefix}/.blocklist" || return 1 # not blocked!
-		local _pattern='//'
-		while read line; do
-			_pattern+=' && !'"/${line}/"
-		done < "${_prefix}/.blocklist"
-		local out=$(awk "${_pattern}"' {print $0}' <<< "${HOSTNAME}")
-		[[ -z "${out}" ]] || return 1  # not blocked!
-		[[ -r "${_prefix}/.blockmsg" ]] || return 0
-		cat "${_prefix}/.blockmsg" 1>&2
-		return 0
-	}
-
 	#......................................................................
 	local args=()
 	local opts=()
@@ -723,23 +717,23 @@ subcommand_load() {
 
 			# extendet module name is either
 			# - group:name or
-			# - group:name:rel_stage or
-			# - rel_stage:name or
-			# - rel_stage:group:name or
-			# - name:rel_stage
+			# - group:name:relstage or
+			# - relstage:name or
+			# - relstage:group:name or
+			# - name:stage
 
 			
 			IFS=':'
 			local -a toks=($m)
 			unset IFS
 			local group=''
-			local rel_stage=''
+			local relstage=''
 			if is_group "${toks[0]}"; then
 				group=${toks[0]}
 				m=${toks[1]}
-				rel_stage=${toks[2]}
+				relstage=${toks[2]}
 			elif is_release_stage "${toks[0]}"; then
-				rel_stage=${toks[0]}
+				relstage=${toks[0]}
 				if is_group "${toks[1]}"; then
 					group=${toks[1]}
 					m=${toks[2]}
@@ -751,9 +745,9 @@ subcommand_load() {
 				m=${toks[0]}
 				if is_group "${toks[1]}"; then
 					group=${toks[1]}
-					rel_stage=${toks[2]}
+					relstage=${toks[2]}
 				else
-					rel_stage=${toks[1]}
+					relstage=${toks[1]}
 					group=${toks[2]}
 				fi
 			fi
@@ -769,20 +763,20 @@ subcommand_load() {
 				        modulepath=( "${mod_root}/${group}" "${modulepath[@]}" )
                                 done
 			fi
-			if [[ -n ${rel_stage} ]]; then
-			        is_release_stage "${rel_stage}" || \
-                                        die_illegal_rel_stage "${rel_stage}"
-				std::append_path UsedReleaseStages "${rel_stage}"
+			if [[ -n ${relstage} ]]; then
+			        is_release_stage "${relstage}" || \
+                                        die_illegal_relstage "${relstage}"
+				std::append_path UsedReleaseStages "${relstage}"
                                 g_env_must_be_saved='yes'
 			fi
 		fi # handle extended module names
 		local moduledir=''
-                find_modulefile current_modulefile rel_stage moduledir "${m}" "${modulepath[@]}"
+                find_modulefile current_modulefile relstage moduledir "${m}" "${modulepath[@]}"
                 if [[ -z ${current_modulefile} ]]; then
 			local fname=$(std::get_abspath "${m}")
 			if [[ -r "${fname}" ]]; then
 				current_modulefile="${fname}"
-				rel_stage='stable'
+				relstage='stable'
 			else
 				local hints=''
 				get_load_hints hints
@@ -803,7 +797,6 @@ subcommand_load() {
 			die_not_a_modulefile "${m}"
 		local prefix=''
 		get_module_prefix prefix "${current_modulefile}"
-		is_blocked "${prefix}" && die_is_blocked "${m}"
                 if [[ -n ${prefix} ]]; then
                         test -r "${prefix}/.info" && cat "$_" 1>&2
 			test -r "${prefix}/.dependencies" && load_dependencies "$_"
@@ -846,17 +839,17 @@ subcommand_load() {
 		fi
 		local msg=''
 		if [[ ${verbosity_lvl} != silent ]] && \
-			   [[ ${rel_stage} != stable ]]; then
+			   [[ ${relstage} != stable ]]; then
 			msg=$(printf "%s %s: %s -- %s" \
 				     "${CMD}" 'load' \
-				     "${rel_stage} module has been loaded" \
+				     "${relstage} module has been loaded" \
 				     "${m}")
 		        std::info "%s" "${msg}"
 		fi
 		msg=$(printf "%s: %s %s %s" \
 			     'load' \
 			     "modulefile=${current_modulefile}" \
-			     "rel-stage=${rel_stage}" \
+			     "rel-stage=${relstage}" \
 			     "user=${USER}")
 		${logger} -t Pmodules "${msg}"
 	done
@@ -1072,14 +1065,14 @@ subcommand_show() {
 #	$4...   module path (fully qualified directory names)
 #
 # return list like
-#	modulename_1 rel_stage_1 modulefile_1 ...
+#	modulename_1 relstage_1 modulefile_1 ...
 #
 get_available_modules() {
         local -n gam_mods="$1"
 	local -r module="$2"
-	local -r used_rel_stages="${3:-${UsedReleaseStages}}"
+	local -r used_relstages="${3:-${UsedReleaseStages}}"
 	shift 3 # in the for loop below we use $@ to loop over module path
-	local    rel_stage
+	local    relstage
 
         local -A dict
 	local -A modulenames
@@ -1133,9 +1126,9 @@ get_available_modules() {
 			[[ "${add}" == 'no' ]] && continue
 			local -A cfg=()
 			get_module_config cfg "${dir}" "${mod}"
-			is_available cfg "${used_rel_stages}" "${os_release}" "${HOSTNAME}" || continue
+			is_available cfg "${used_relstages}" "${os_release}" "${HOSTNAME}" || continue
 
-			gam_mods+=( "${mod}" "${cfg['rel_stage']}" "${dir}/${mod}" "${ol}" )
+			gam_mods+=( "${mod}" "${cfg['relstage']}" "${dir}/${mod}" "${ol}" )
                         dict[${sdirs}/${mod}]=1
 		done < <(${find} -L "${dir_entries[@]}" \
 				 \( -type f -o -type l \) \
@@ -1164,7 +1157,7 @@ get_available_modules() {
 #       
 find_modulefile() {
 	local -n fm_modulefile="$1"
-	local -n fm_rel_stage="$2"
+	local -n fm_relstage="$2"
 	local -n fm_dir="$3"
 	local -r module="$4"
 	local -a dirs=("${@:5}")
@@ -1194,7 +1187,7 @@ find_modulefile() {
 				is_available cfg "${ReleaseStages}" "${os_release}" "${HOSTNAME}" || continue
 
 				fm_modulefile="${dir}/${mod}"
-				fm_rel_stage="${cfg['rel_stage']}"
+				fm_relstage="${cfg['relstage']}"
 				fm_dir="${dir}"
                                 return 0
                         done
@@ -1224,7 +1217,7 @@ find_modulefile() {
 				get_module_config cfg "${dir}" "${mod}"
 				is_available cfg "${ReleaseStages}" "${os_release}" "${HOSTNAME}" || continue
 				fm_modulefile="${dir}/${mod}"
-				fm_rel_stage="${cfg['rel_stage']}"
+				fm_relstage="${cfg['relstage']}"
 				fm_dir="${dir}"
 				return 0
                         done
@@ -1296,13 +1289,13 @@ subcommand_avail() {
 		local -i i=0
 		for (( i=0; i<${#mods[@]}; i+=4 )); do
 			local mod=${mods[i]}
-			local rel_stage=${mods[i+1]}
-			case ${rel_stage} in
+			local relstage=${mods[i+1]}
+			case ${relstage} in
 				stable )
 					out=''
 					;;
 				* )
-					out="${rel_stage}"
+					out="${relstage}"
 					;;
 			esac
 			printf "%-20s\t%s\n" "${mod}" "${out}" 1>&2
@@ -1323,13 +1316,13 @@ subcommand_avail() {
 		output_header "$1"
 		for (( i=0; i<${#mods[@]}; i+=4 )); do
 			local mod=${mods[i]}
-			local rel_stage=${mods[i+1]}
-			case ${rel_stage} in
+			local relstage=${mods[i+1]}
+			case ${relstage} in
 				stable )
 					out=''
 					;;
 				* )
-					out=${rel_stage}
+					out=${relstage}
 					;;
 			esac
 			printf "%-20s\t%s\n" "${mod}" "${out}" 1>&2
@@ -1346,13 +1339,13 @@ subcommand_avail() {
 		local -i max_length=1
 		for ((i=0; i<${#mods[@]}; i+=4)); do
 			if [[ ${verbosity_lvl} == 'verbose' ]]; then
-			        local  rel_stage=${mods[i+1]}
-			        case ${rel_stage} in
+			        local  relstage=${mods[i+1]}
+			        case ${relstage} in
 					stable )
 						mod="${mods[i]}"
 						;;
 					* )
-						mod="${mods[i]}(${rel_stage:0:1})"
+						mod="${mods[i]}(${relstage:0:1})"
 						;;
 				esac
 			else
@@ -1387,7 +1380,7 @@ subcommand_avail() {
 	#......................................................................
 	local pattern=()
 	local output_function='human_readable_output'
-	local opt_use_rel_stages="${UsedReleaseStages}"
+	local opt_use_relstages="${UsedReleaseStages}"
 	local -A opt_groups=()
 	local val=''
 	while (($# > 0)); do
@@ -1396,7 +1389,7 @@ subcommand_avail() {
                                 print_help "${subcommand}"
                                 ;;
 			-a | --all | --all-release-stages )
-				opt_use_rel_stages="${ReleaseStages}"
+				opt_use_relstages="${ReleaseStages}"
 				;;
 			-h | --human )
 				output_function='human_readable_output'
@@ -1484,7 +1477,7 @@ subcommand_avail() {
 			get_available_modules \
 				mods \
 				"${string}*" \
-                                "${opt_use_rel_stages}" \
+                                "${opt_use_relstages}" \
 				"${path[@]}"
 
 			[[ ${#mods[@]} == 0 ]] && continue
@@ -2471,17 +2464,17 @@ subcommand_search() {
 		
 		# get and print all available modules in $mpath
 		# with respect to the requested release stage
-		# tmpfile: module/version rel_stage group dependencies...
+		# tmpfile: module/version relstage group dependencies...
 		local mods
 		get_available_modules \
 			mods \
 			"${module}" \
-			"${opt_use_rel_stages}" \
+			"${opt_use_relstages}" \
 			"${modulepath[@]}"
 		local i=0
 		for (( i=0; i<${#mods[@]}; i+=4 )); do
 			local name=${mods[i]}
-			local rel_stage=${mods[i+1]}
+			local relstage=${mods[i+1]}
 			local modulefile=${mods[i+2]}
 			local ol=${mods[i+3]}
 			
@@ -2511,7 +2504,7 @@ subcommand_search() {
 				unset IFS
 			fi
 			
-			echo ${name} ${rel_stage} ${group} ${modulefile} \
+			echo ${name} ${relstage} ${group} ${modulefile} \
 			     ${ol} \
                              ${deps[@]} >> "${tmpfile}"
 		done
@@ -2548,7 +2541,7 @@ subcommand_search() {
                                                  "${CMD}" 'search' \
                                                  "illegal release stage" \
                                                  "${arg}"
-				opt_use_rel_stages+="${arg}:"
+				opt_use_relstages+="${arg}:"
 				;;
 			--with | --with=* )
                                 if [[ "$1" == --with ]]; then
@@ -2570,7 +2563,7 @@ subcommand_search() {
                                 done
 				;;
 			-a | --all-releases-stages )
-				opt_use_rel_stages+="${ReleaseStages}"
+				opt_use_relstages+="${ReleaseStages}"
 				;;
 			--src | --src=*)
                                 if [[ "$1" == --src ]]; then
@@ -2632,8 +2625,8 @@ subcommand_search() {
 		done
 	fi
 
-	if [[ "${opt_use_rel_stages}" == ":" ]]; then
-                opt_use_rel_stages=":${UsedReleaseStages}:"
+	if [[ "${opt_use_relstages}" == ":" ]]; then
+                opt_use_relstages=":${UsedReleaseStages}:"
 	fi
 
 	if [[ ${#modules[@]} == 0 ]]; then
@@ -3399,6 +3392,10 @@ case "$1" in
 esac
 shift
 
+debug(){
+	:
+}
+
 # parse agruments till and including the sub-command
 declare -a opts=()
 while (( $# > 0 )); do
@@ -3410,6 +3407,11 @@ while (( $# > 0 )); do
 			print_help 'version'
 			;;
 		--debug )
+			debug(){
+				echo "DEBUG: " "$@" 1>&2
+			}
+			;;
+		--verbose )
 			set -x
 			;;
 		'' )
diff --git a/Pmodules/yq.x86_64_Linux b/Pmodules/yq.x86_64_Linux
index 9e2a58f..1d884df 100755
Binary files a/Pmodules/yq.x86_64_Linux and b/Pmodules/yq.x86_64_Linux differ