diff --git a/build_functions.sh b/build_functions.sh
index 8d30c07..15c06e3 100644
--- a/build_functions.sh
+++ b/build_functions.sh
@@ -209,8 +209,24 @@ build_install () {
 	make install 2>&1 | tee "${LOG}/make-install.log"
 }
 
+module_capture_prereq () {
+	# This function returns the module system "prereq" lines
+	# built from the curently loaded modules listed in `$LOADEDMODULES`
+	MODULES="${LOADEDMODULES:-}"
+	for dep in ${MODULES//:/ }; do
+		if echo "$dep" | grep "Builder" >/dev/null; then
+			# nothing should ever automatically depend on builder
+			# so we skip this dependency.
+			continue;
+		fi
+		echo -n "prereq $dep\\n"
+	done
+}
+
 module_install () {
 	AUTOMATIC_BUILD_WARNING=" This file was automatically produced by Builder.\n# Any changes may be overwritten without notice.\n#\n# Please see ${BUILDER_PATH} for details."
+
+	PREREQ_DEPENDS="$(module_capture_prereq)"
 	if [ -r "${PLAN}.module" ]; then
 		module_path="${MODULE_INSTALL_PATH}/${PACKAGE}/${VERSION}/${VARIANT}"
 		#PYTHON_SCRIPTS="$(python -c "import sysconfig; print(sysconfig.get_path('scripts'))")"
@@ -221,7 +237,7 @@ module_install () {
 		mkdir -pv "$(dirname "${module_path}")"
 		module="$(cat "${PLAN}.module")"
 		if version_gt $BASH_VERSION 4.4; then
-			echo "${module@P}" >"${module_path}"
+			echo -e "${module@P}" >"${module_path}"
 		else
 			# this is a bad substitute for the power of the bash>4.4 notation.
 			echo "${module}" | sed \
@@ -243,6 +259,7 @@ module_install () {
 			    -e "s%\${\?TARGET}\?%$TARGET%g" \
 			    -e "s%\${\?BUILD}\?%$BUILD%g" \
 			    -e "s%\${\?LOG}\?%$LOG%g" \
+			    -e "s%\${\?PREREQ_DEPENDS}\?%$PREREQ_DEPENDS%g" \
 			    -e "s%\${\?VIRTUAL_ENV}\?%${VIRTUAL_ENV:-/}%g" \
 			    -e 's%__NOT_BUILDER_DOLLAR__%$%g' \
 			       > "${module_path}"
diff --git a/doc/module-dependencies b/doc/module-dependencies
new file mode 100644
index 0000000..5c1143f
--- /dev/null
+++ b/doc/module-dependencies
@@ -0,0 +1,19 @@
+# Module files and Dependencies
+
+Builder does explicitly not track dependencies between packages, but is designed
+to work with what is there. This is necessary to be able to integrate well with
+different environments on each machine. What builder can do, however, is to track
+which modules where loaded during the build time. It is (for now) assumed that
+
+* run-time dependencies are at least a sub-set of the build-time dependencies, 
+  so that requiring build-time deps at run-time provides all package requirements,
+  and
+* build-time loaded modules are also available at run-time (not a given, if
+  packages are built on a head node, but run on a compute node, for example).
+
+Additional points to note are
+
+* required modules are different on all systems, so module-names can not be
+  hard-coded in planfiles or modulefile templates.
+* Builder is not designed for cross-compiles.
+
diff --git a/plans/bats/1.2.1/default b/plans/bats/1.2.1/default
new file mode 100644
index 0000000..6eee4c3
--- /dev/null
+++ b/plans/bats/1.2.1/default
@@ -0,0 +1,31 @@
+#
+# This file is part of Builder.
+#
+# Builder is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Builder is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Builder.  If not, see <https://www.gnu.org/licenses/>.
+#
+URL="https://github.com/bats-core/bats-core/archive/v${VERSION}.tar.gz"
+MD5SUM="e0efccc6345218d40c39678d1c89e67e"
+SHA256SUM="91c49b1fe6f0656c46491929ed728f8dfa9a96df0cce294963e8c6082bff87a2"
+
+build_prepare() {
+	log_status ">>> nothing to prepare"
+}
+build_package() {
+	log_status ">>> nothing to build"
+}
+build_install () {
+	log_status ">>> installing..."
+	cd "${SOURCE}"
+	./install.sh "${TARGET}" 2>&1 | tee "${LOG}/make-install.log"
+}
diff --git a/plans/bats/1.2.1/default.module b/plans/bats/1.2.1/default.module
new file mode 100644
index 0000000..f1769a8
--- /dev/null
+++ b/plans/bats/1.2.1/default.module
@@ -0,0 +1,23 @@
+#%Module1.0#####################################################################
+##
+set     INSTALLDIR      "${TARGET}"
+
+proc ModulesHelp { } {
+        puts stderr "
+   Bats is a TAP-compliant testing framework for Bash. It provides a simple way
+   to verify that the UNIX programs you write behave as expected.
+
+   A Bats test file is a Bash script with special syntax for defining test
+   cases. Under the hood, each test case is just a function with a description.
+
+   See https://github.com/bats-core/bats-core#bats-core-bash-automated-testing-system-2018
+"
+}
+
+module-whatis   "Bash testing framework (${VERSION})"
+
+conflict ${PACKAGE}
+${PREREQ_DEPENDS}
+
+prepend-path    PATH    \$INSTALLDIR/bin
+prepend-path    MANPATH \$INSTALLDIR/share/man
diff --git a/plans/nest-simulator/2.20.0/default.module b/plans/nest-simulator/2.20.0/default.module
index c251809..a023fbb 100644
--- a/plans/nest-simulator/2.20.0/default.module
+++ b/plans/nest-simulator/2.20.0/default.module
@@ -30,6 +30,7 @@ INSTALLDIR:  	\$INSTALLDIR"
 module-whatis   "NEST spiking neural network simulator, version ${VERSION} (${VARIANT} build)"
 
 conflict ${PACKAGE}
+${PREREQ_DEPENDS}
 
 ################################################################################
 # from \$INSTALLDIR/bin/nest_vars.sh