diff --git a/Compiler/clhep/build b/Compiler/clhep/build
index 91eb599..6e021f3 100755
--- a/Compiler/clhep/build
+++ b/Compiler/clhep/build
@@ -1,20 +1,2 @@
 #!/usr/bin/env modbuild
 
-pbuild::set_download_url "https://proj-clhep.web.cern.ch/proj-clhep/dist1/$P-${V_PKG}.tgz"
-pbuild::add_to_group 'Compiler'
-
-pbuild::install_docfiles 'ChangeLog'
-pbuild::install_docfiles 'compilers.txt'
-pbuild::install_docfiles 'COPYING'
-pbuild::install_docfiles 'COPYING.LESSER'
-pbuild::install_docfiles 'README.md'
-
-pbuild::post_prep() {
-	mv CLHEP/* .
-}
-
-# Local Variables:
-# mode: sh
-# sh-basic-offset: 8
-# tab-width: 8
-# End:
diff --git a/Compiler/clhep/files/config.yaml b/Compiler/clhep/files/config.yaml
new file mode 100644
index 0000000..34fd8eb
--- /dev/null
+++ b/Compiler/clhep/files/config.yaml
@@ -0,0 +1,23 @@
+---
+# yamllint disable rule:line-length
+format: 1
+clhep:
+  defaults:
+    group: Compiler
+    overlay: base
+    systems: [rhel7, rhel8, rhel9]
+    docfiles: [AUTHORS, LICENSE, NEWS, README]
+    configure_with: cmake
+    build_requires: ['cmake/3.26.3']
+    relstage: stable
+    urls:
+      - url: https://proj-clhep.web.cern.ch/proj-clhep/dist1/clhep-2.4.7.1.tgz
+  shasums:
+    clhep-2.4.7.1.tgz: 1c8304a7772ac6b99195f1300378c6e3ddf4ad07c85d64a04505652abb8a55f9
+
+  versions:
+    2.4.7.1:
+      variants:
+        - systems: [merlin-*, ra-*]
+          group_deps:
+            compiler: {gcc: [13.1.0]}
diff --git a/Compiler/geant4/build b/Compiler/geant4/build
index b381e4a..6e021f3 100755
--- a/Compiler/geant4/build
+++ b/Compiler/geant4/build
@@ -1,27 +1,2 @@
 #!/usr/bin/env modbuild
 
-declare -r VERSION=${V_MAJOR}.$(printf '%02d' ${V_MINOR})
-pbuild::set_download_url "http://cern.ch/geant4-data/releases/$P.${VERSION}.tar.gz"
-pbuild::add_to_group 'Compiler'
-
-#pbuild::install_docfiles 'ChangeLog'
-#pbuild::install_docfiles 'compilers.txt'
-#pbuild::install_docfiles 'COPYING'
-#pbuild::install_docfiles 'COPYING.LESSER'
-#pbuild::install_docfiles 'README.md'
-
-pbuild::pre_configure() {
-	pbuild::add_configure_args "-DCMAKE_INSTALL_PREFIX=${PREFIX}"
-	pbuild::add_configure_args "-DGEANT4_USE_SYSTEM_CLHEP=ON"
-	pbuild::add_configure_args "-DPC_EXPAT_INCLUDE_DIRS=${LIBEXPAT_INCLUDE_DIR}"
-	pbuild::add_configure_args "-DGEANT4_INSTALL_DATA=ON"
-	if pbuild::use_flag 'multithreaded'; then
-		pbuild::add_configure_args "-DGEANT4_BUILD_MULTITHREADED=ON"
-	fi
-}
-
-# Local Variables:
-# mode: sh
-# sh-basic-offset: 8
-# tab-width: 8
-# End:
diff --git a/Compiler/geant4/files/config.yaml b/Compiler/geant4/files/config.yaml
new file mode 100644
index 0000000..a1f1b8b
--- /dev/null
+++ b/Compiler/geant4/files/config.yaml
@@ -0,0 +1,31 @@
+---
+# yamllint disable rule:line-length
+format: 1
+geant4:
+  defaults:
+    group: Compiler
+    overlay: base
+    docfiles: [AUTHORS, LICENSE, NEWS, README]
+    configure_with: cmake
+    urls:
+      - url: https://gitlab.cern.ch/${P}/${P}/-/archive/v${V_PKG}/${P}-v${V_PKG}.tar.gz
+  shasums:
+    geant4-v11.2.1.tar.gz: 76c9093b01128ee2b45a6f4020a1bcb64d2a8141386dea4674b5ae28bcd23293
+
+  versions:
+    11.2.1:
+      variants:
+        - systems: [merlin-.*, ra-.*]
+          group_deps:
+            compiler: {gcc: [13.1.0]}
+          build_requires:
+            - clhep/2.4.7.1
+            - libexpat/2.2.6
+            - cmake/3.26.3
+          configure_args: 
+            - -DGEANT4_USE_SYSTEM_CLHEP=ON
+            - -DPC_EXPAT_INCLUDE_DIRS=${LIBEXPAT_INCLUDE_DIR}
+            - -DGEANT4_INSTALL_DATA=ON
+            - -DGEANT4_BUILD_MULTITHREADED=ON
+          relstage: stable
+
diff --git a/Libraries/libexpat/build b/Libraries/libexpat/build
index bbca686..6e021f3 100755
--- a/Libraries/libexpat/build
+++ b/Libraries/libexpat/build
@@ -1,19 +1,2 @@
 #!/usr/bin/env modbuild
 
-pbuild::set_download_url "https://github.com/$P/$P/releases/download/R_${V_PKG//./_}/expat-${V_PKG}.tar.bz2"
-pbuild::add_to_group 'Libraries'
-
-#pbuild::compile_in_sourcetree
-
-pbuild::install_docfiles 'AUTHORS'
-pbuild::install_docfiles 'Changes'
-pbuild::install_docfiles 'COPYING'
-pbuild::install_docfiles 'README.md'
-
-pbuild::pre_configure() {
-	pbuild::add_configure_args "--disable-shared"
-	pbuild::add_configure_args "--with-pic"
-}
-
-pbuild::make_all
-
diff --git a/Libraries/libexpat/files/config.yaml b/Libraries/libexpat/files/config.yaml
new file mode 100644
index 0000000..e8f979d
--- /dev/null
+++ b/Libraries/libexpat/files/config.yaml
@@ -0,0 +1,26 @@
+format: 1
+libexpat:
+  defaults:
+    group: Libraries
+    overlay: base 
+    relstage: stable
+    configure_args: []
+    docfiles:
+      - AUTHOR'
+      - Changes
+      - COPYING
+      - README.md
+    urls:
+      - url: https://github.com/$P/$P/releases/download/R_${V_PKG//./_}/expat-${V_PKG}.tar.bz2
+    configure_args:
+      - --disable-shared
+      - --with-pic
+
+  shasums:
+    libexpat-2.2.6.tar.bz2: 0019dfc4b32d63c1392aa264aed2253c1e0c2fb09216f8e2cc269bbfb8bb49b5
+
+  versions:
+    2.2.6:
+      config:
+        relstage: stable
+
diff --git a/Libraries/libexpat/files/variants b/Libraries/libexpat/files/variants
deleted file mode 100644
index cb1a705..0000000
--- a/Libraries/libexpat/files/variants
+++ /dev/null
@@ -1 +0,0 @@
-libexpat/2.2.6		unstable