diff --git a/bin/Mamfile_rm_unused_vars b/bin/Mamfile_rm_unused_vars
new file mode 100755
index 000000000..07b78e54e
--- /dev/null
+++ b/bin/Mamfile_rm_unused_vars
@@ -0,0 +1,30 @@
+#!/usr/bin/env sh
+IFS=''; set -fCu  # safe mode: no split/glob = no quoting headaches
+CCn='
+'  # newline
+let() { return $((!($1))); }
+
+# Remove unused variable definitions from a Mamfile.
+# Usage: Mamfile_rm_unused_vars <Mamfile >Mamfile.new
+#
+# Should work on all current POSIX compliant shells.
+# By Martijn Dekker <martijn@inlv.org>, 2021. Public domain.
+#
+# All variables are declared with 'setv' and they are used if an expansion
+# of the form ${varname} exists (the braces are mandatory in Mamfiles).
+
+mamfile=$(let $# && cat "$1" || cat)
+vars=$(printf '%s\n' $mamfile | awk '$1 == "setv" { print $2; }')
+rm_unused_ere=
+IFS=$CCn; for varname in $vars; do IFS=
+	case $mamfile in
+	*"\${$varname}"* )
+		;;
+	* )	# add with '|' separator for Extended Regular Expression
+		rm_unused_ere="${rm_unused_ere:+$rm_unused_ere|}setv[[:blank:]]+$varname([[:blank:]]|$)" ;;
+	esac
+done
+case $rm_unused_ere in
+'')	printf '%s\n' $mamfile ;;
+*)	printf '%s\n' $mamfile | grep -vE $rm_unused_ere ;;
+esac
diff --git a/src/cmd/INIT/Mamfile b/src/cmd/INIT/Mamfile
index 8b5f58a79..cc37fd8be 100644
--- a/src/cmd/INIT/Mamfile
+++ b/src/cmd/INIT/Mamfile
@@ -10,38 +10,13 @@ note * http://web.archive.org/web/20041227143022/http://www2.research.att.com/~g
 note *
 setv INSTALLROOT ../../..
 setv PACKAGEROOT ../../../../..
-setv AR ${mam_cc_AR} ${mam_cc_AR_ARFLAGS}
-setv ARFLAGS rc
-setv AS as
-setv ASFLAGS
 setv CC cc
 setv mam_cc_FLAGS
 setv KSH_RELFLAGS
 setv CCFLAGS ${-debug-symbols?1?${mam_cc_DEBUG} -D_BLD_DEBUG?${mam_cc_OPTIMIZE}?}
 setv CCLDFLAGS ${-strip-symbols?1?${mam_cc_LD_STRIP}??}
 setv COTEMP $$
-setv CPIO cpio
-setv CPIOFLAGS
-setv CPP "${CC} -E"
-setv F77 f77
-setv HOSTCC ${CC}
-setv IGNORE
-setv LD ld
 setv LDFLAGS
-setv LEX lex
-setv LEXFLAGS
-setv LPR lpr
-setv LPRFLAGS
-setv M4FLAGS
-setv NMAKE nmake
-setv NMAKEFLAGS
-setv PR pr
-setv PRFLAGS
-setv SHELL /bin/sh
-setv SILENT
-setv TAR tar
-setv YACC yacc
-setv YACCFLAGS -d
 make ${PACKAGEROOT}/lib/package/ast.lic
 done ${PACKAGEROOT}/lib/package/ast.lic
 make install
@@ -50,7 +25,6 @@ make install
 		done hurl.sh
 		meta hurl %.sh>% hurl.sh hurl
 		prev hurl.sh
-		setv LICENSE -DLICENSE="since=2003,author=gsf"
 		exec - case static,port:$OPTIND:$RANDOM in
 		exec - ?*:*:*|*::*|*:*:$RANDOM)
 		exec - ;;
@@ -88,7 +62,6 @@ make install
 		done iffe.sh
 		meta iffe %.sh>% iffe.sh iffe
 		prev iffe.sh
-		setv LICENSE -DLICENSE="since=1994,author=gsf+kpv"
 		exec - case static,port:$OPTIND:$RANDOM in
 		exec - ?*:*:*|*::*|*:*:$RANDOM)
 		exec - ;;
@@ -126,7 +99,6 @@ make install
 		done mktest.sh
 		meta mktest %.sh>% mktest.sh mktest
 		prev mktest.sh
-		setv LICENSE -DLICENSE="since=2005,author=gsf"
 		exec - case static,port:$OPTIND:$RANDOM in
 		exec - ?*:*:*|*::*|*:*:$RANDOM)
 		exec - ;;
@@ -201,7 +173,6 @@ make install
 		done regress.sh
 		meta regress %.sh>% regress.sh regress
 		prev regress.sh
-		setv LICENSE -DLICENSE="since=1995,author=gsf"
 		exec - case static,port:$OPTIND:$RANDOM in
 		exec - ?*:*:*|*::*|*:*:$RANDOM)
 		exec - ;;
@@ -239,7 +210,6 @@ make install
 		done rt.sh
 		meta rt %.sh>% rt.sh rt
 		prev rt.sh
-		setv LICENSE -DLICENSE="since=2005,author=gsf"
 		exec - case static,port:$OPTIND:$RANDOM in
 		exec - ?*:*:*|*::*|*:*:$RANDOM)
 		exec - ;;
@@ -314,7 +284,6 @@ make install
 		done ditto.sh
 		meta ditto %.sh>% ditto.sh ditto
 		prev ditto.sh
-		setv LICENSE -DLICENSE="since=2001,author=gsf+ek"
 		exec - case static,port:$OPTIND:$RANDOM in
 		exec - ?*:*:*|*::*|*:*:$RANDOM)
 		exec - ;;
@@ -352,7 +321,6 @@ make install
 		done execrate.sh
 		meta execrate %.sh>% execrate.sh execrate
 		prev execrate.sh
-		setv LICENSE -DLICENSE="since=2002,author=gsf"
 		exec - case static,port:$OPTIND:$RANDOM in
 		exec - ?*:*:*|*::*|*:*:$RANDOM)
 		exec - ;;
diff --git a/src/cmd/builtin/Mamfile b/src/cmd/builtin/Mamfile
index 8666e018a..873ad99d0 100644
--- a/src/cmd/builtin/Mamfile
+++ b/src/cmd/builtin/Mamfile
@@ -10,44 +10,15 @@ note * http://web.archive.org/web/20041227143022/http://www2.research.att.com/~g
 note *
 setv INSTALLROOT ../../..
 setv PACKAGE_ast_INCLUDE ${INSTALLROOT}/include/ast
-setv PACKAGE_ast_LIB ${INSTALLROOT}/lib
 setv PACKAGE_cmd ${INSTALLROOT}
-setv PACKAGE_cmd_INCLUDE ${PACKAGE_cmd}/include
-setv PACKAGE_cmd_LIB ${PACKAGE_cmd}/lib
 setv PACKAGEROOT ../../../../..
-setv AR ${mam_cc_AR} ${mam_cc_AR_ARFLAGS}
-setv ARFLAGS rc
-setv AS as
-setv ASFLAGS
 setv CC cc
 setv mam_cc_FLAGS
 setv KSH_RELFLAGS
 setv CCFLAGS ${-debug-symbols?1?${mam_cc_DEBUG} -D_BLD_DEBUG?${mam_cc_OPTIMIZE}?}
 setv CCLDFLAGS ${-strip-symbols?1?${mam_cc_LD_STRIP}??}
-setv COTEMP $$
-setv CPIO cpio
-setv CPIOFLAGS
-setv CPP "${CC} -E"
-setv F77 f77
-setv HOSTCC ${CC}
 setv IFFEFLAGS
-setv IGNORE
-setv LD ld
 setv LDFLAGS
-setv LEX lex
-setv LEXFLAGS
-setv LPR lpr
-setv LPRFLAGS
-setv M4FLAGS
-setv NMAKE nmake
-setv NMAKEFLAGS
-setv PR pr
-setv PRFLAGS
-setv SHELL /bin/sh
-setv SILENT
-setv TAR tar
-setv YACC yacc
-setv YACCFLAGS -d
 make ${PACKAGEROOT}/lib/package/ast.lic
 done ${PACKAGEROOT}/lib/package/ast.lic
 make .INIT
@@ -81,12 +52,9 @@ make install
 			done pty.c
 			meta pty.o %.c>%.o pty.c pty
 			prev pty.c
-			setv CMD_STANDALONE -DCMD_STANDALONE="b_pty"
-			setv LICENSE -DLICENSE="since=2001,author=gsf+dgk"
 			exec - ${CC} ${mam_cc_FLAGS} ${KSH_RELFLAGS} ${CCFLAGS} -I. -I${PACKAGE_ast_INCLUDE} -DERROR_CATALOG=\""builtin"\" -D_PACKAGE_ast -DCMD_STANDALONE=b_pty -c pty.c
 		done pty.o generated
 		bind -lutil dontcare
-		setv CMD_STANDALONE -DCMD_STANDALONE="b_pty"
 		exec - ${CC} ${CCLDFLAGS} ${mam_cc_FLAGS} ${KSH_RELFLAGS} ${CCFLAGS} ${LDFLAGS} -lm ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -o pty pty.o ${mam_libutil} ${mam_libast} ${mam_libcmd}
 	done pty generated
 	make ${INSTALLROOT}/bin
diff --git a/src/cmd/ksh93/Mamfile b/src/cmd/ksh93/Mamfile
index 62da18b49..cb560713a 100644
--- a/src/cmd/ksh93/Mamfile
+++ b/src/cmd/ksh93/Mamfile
@@ -10,12 +10,8 @@ note * http://web.archive.org/web/20041227143022/http://www2.research.att.com/~g
 note *
 setv INSTALLROOT ../../..
 setv PACKAGE_ast_INCLUDE ${INSTALLROOT}/include/ast
-setv PACKAGE_ast_LIB ${INSTALLROOT}/lib
 setv PACKAGEROOT ../../../../..
 setv AR ${mam_cc_AR} ${mam_cc_AR_ARFLAGS}
-setv ARFLAGS rc
-setv AS as
-setv ASFLAGS
 setv CC cc
 setv mam_cc_FLAGS
 setv KSH_RELFLAGS
@@ -23,30 +19,9 @@ setv KSH_SHOPTFLAGS
 setv CCFLAGS ${-debug-symbols?1?${mam_cc_DEBUG} -D_BLD_DEBUG?${mam_cc_OPTIMIZE}?}
 setv CCLDFLAGS ${-strip-symbols?1?${mam_cc_LD_STRIP}??}
 setv COTEMP $$
-setv CPIO cpio
-setv CPIOFLAGS
-setv CPP "${CC} -E"
-setv F77 f77
-setv HOSTCC ${CC}
 setv IFFEFLAGS
-setv IGNORE
-setv LD ld
 setv LDFLAGS
-setv LEX lex
-setv LEXFLAGS
-setv LPR lpr
-setv LPRFLAGS
-setv M4FLAGS
-setv NMAKE nmake
-setv NMAKEFLAGS
-setv PR pr
-setv PRFLAGS
 setv SH_DICT \"libshell\"
-setv SHELL /bin/sh
-setv SILENT
-setv TAR tar
-setv YACC yacc
-setv YACCFLAGS -d
 make ${PACKAGEROOT}/lib/package/ast.lic
 done ${PACKAGEROOT}/lib/package/ast.lic
 make install
@@ -1412,9 +1387,6 @@ make install
 			meta shcomp.o %.c>%.o sh/shcomp.c shcomp
 			prev sh/shcomp.c
 			prev SHOPT.sh
-			setv CC.DLL -UCC.DLL
-			setv _BLD_shell -U_BLD_shell
-			setv _BLD_DLL -U_BLD_DLL
 			exec - ${CC} ${mam_cc_FLAGS} ${KSH_RELFLAGS} ${KSH_SHOPTFLAGS} ${CCFLAGS} -I. -Iinclude -I${PACKAGE_ast_INCLUDE} -DSH_DICT=${SH_DICT} -D_API_ast=20100309 -D_PACKAGE_ast -DERROR_CONTEXT_T=Error_context_t -c sh/shcomp.c
 		done shcomp.o generated
 		prev libshell.a archive
@@ -1422,7 +1394,6 @@ make install
 		prev +li
 		prev ${mam_libsocket}
 		prev ${mam_libsecdb}
-		setv CC.DLL -UCC.DLL
 		exec - ${CC} ${CCLDFLAGS} ${mam_cc_FLAGS} ${KSH_RELFLAGS} ${KSH_SHOPTFLAGS} ${CCFLAGS} ${LDFLAGS} ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -o shcomp shcomp.o ${mam_libshell} ${mam_libnsl} ${mam_libast}
 	done shcomp generated
 	make suid_exec
@@ -1438,15 +1409,12 @@ make install
 			meta suid_exec.o %.c>%.o sh/suid_exec.c suid_exec
 			prev sh/suid_exec.c
 			prev SHOPT.sh
-			setv CC.DLL -UCC.DLL
-			setv _BLD_shell -U_BLD_shell
 			exec - ${CC} ${mam_cc_FLAGS} ${KSH_RELFLAGS} ${KSH_SHOPTFLAGS} ${CCFLAGS} -I. -Iinclude -I${PACKAGE_ast_INCLUDE} -DERROR_CONTEXT_T=Error_context_t -D_API_ast=20100309 -D_PACKAGE_ast -c sh/suid_exec.c
 		done suid_exec.o generated
 		prev +ljobs
 		prev +li
 		prev ${mam_libsocket}
 		prev ${mam_libsecdb}
-		setv CC.DLL -UCC.DLL
 		exec - ${CC} ${CCLDFLAGS} ${mam_cc_FLAGS} ${KSH_RELFLAGS} ${KSH_SHOPTFLAGS} ${CCFLAGS} ${LDFLAGS} -lm ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -o suid_exec suid_exec.o ${mam_libast} ${mam_libnsl} ${mam_libast}
 	done suid_exec generated
 	make shell
@@ -1558,19 +1526,16 @@ make install
 		prev ${INSTALLROOT}/fun
 		make fun/dirs
 		done fun/dirs
-		setv mode -Dmode="+x"
 		exec - test '' = 'fun/dirs' || ${STDCMP} 2>/dev/null -s fun/dirs ${INSTALLROOT}/fun/dirs || { ${STDMV} ${INSTALLROOT}/fun/dirs ${INSTALLROOT}/fun/dirs.old 2>/dev/null || true; ${STDCP} fun/dirs ${INSTALLROOT}/fun/dirs && chmod ugo+x ${INSTALLROOT}/fun/dirs ;}
 	done ${INSTALLROOT}/fun/dirs generated
 	make ${INSTALLROOT}/fun/popd
 		make fun/popd
 		done fun/popd
-		setv mode -Dmode="+x"
 		exec - test '' = 'fun/popd' || ${STDCMP} 2>/dev/null -s fun/popd ${INSTALLROOT}/fun/popd || { ${STDMV} ${INSTALLROOT}/fun/popd ${INSTALLROOT}/fun/popd.old 2>/dev/null || true; ${STDCP} fun/popd ${INSTALLROOT}/fun/popd && chmod ugo+x ${INSTALLROOT}/fun/popd ;}
 	done ${INSTALLROOT}/fun/popd generated
 	make ${INSTALLROOT}/fun/pushd
 		make fun/pushd
 		done fun/pushd
-		setv mode -Dmode="+x"
 		exec - test '' = 'fun/pushd' || ${STDCMP} 2>/dev/null -s fun/pushd ${INSTALLROOT}/fun/pushd || { ${STDMV} ${INSTALLROOT}/fun/pushd ${INSTALLROOT}/fun/pushd.old 2>/dev/null || true; ${STDCP} fun/pushd ${INSTALLROOT}/fun/pushd && chmod ugo+x ${INSTALLROOT}/fun/pushd ;}
 	done ${INSTALLROOT}/fun/pushd generated
 done install virtual
diff --git a/src/lib/libast/Mamfile b/src/lib/libast/Mamfile
index 2d2e90090..fa8dd8b37 100644
--- a/src/lib/libast/Mamfile
+++ b/src/lib/libast/Mamfile
@@ -11,38 +11,14 @@ note *
 setv INSTALLROOT ../../..
 setv PACKAGEROOT ../../../../..
 setv AR ${mam_cc_AR} ${mam_cc_AR_ARFLAGS}
-setv ARFLAGS rc
-setv AS as
-setv ASFLAGS
 setv CC cc
 setv mam_cc_FLAGS ${mam_cc_DLL} -D_BLD_ast
 setv KSH_RELFLAGS
 setv CCFLAGS ${-debug-symbols?1?${mam_cc_DEBUG} -D_BLD_DEBUG?${mam_cc_OPTIMIZE}?}
 setv CCLDFLAGS ${-strip-symbols?1?${mam_cc_LD_STRIP}??}
 setv COTEMP $$
-setv CPIO cpio
-setv CPIOFLAGS
-setv CPP "${CC} -E"
-setv F77 f77
-setv HOSTCC ${CC}
 setv IFFEFLAGS
-setv IGNORE
-setv LD ld
 setv LDFLAGS
-setv LEX lex
-setv LEXFLAGS
-setv LPR lpr
-setv LPRFLAGS
-setv M4FLAGS
-setv NMAKE nmake
-setv NMAKEFLAGS
-setv PR pr
-setv PRFLAGS
-setv SHELL /bin/sh
-setv SILENT
-setv TAR tar
-setv YACC yacc
-setv YACCFLAGS -d
 make ${PACKAGEROOT}/lib/package/ast.lic
 done ${PACKAGEROOT}/lib/package/ast.lic
 make install
diff --git a/src/lib/libcmd/Mamfile b/src/lib/libcmd/Mamfile
index 64aaef091..5eba66e44 100644
--- a/src/lib/libcmd/Mamfile
+++ b/src/lib/libcmd/Mamfile
@@ -10,41 +10,15 @@ note * http://web.archive.org/web/20041227143022/http://www2.research.att.com/~g
 note *
 setv INSTALLROOT ../../..
 setv PACKAGE_ast_INCLUDE ${INSTALLROOT}/include/ast
-setv PACKAGE_ast_LIB ${INSTALLROOT}/lib
 setv PACKAGEROOT ../../../../..
 setv AR ${mam_cc_AR} ${mam_cc_AR_ARFLAGS}
-setv ARFLAGS rc
-setv AS as
-setv ASFLAGS
 setv CC cc
 setv mam_cc_FLAGS ${mam_cc_DLL}
 setv KSH_RELFLAGS
 setv CCFLAGS ${-debug-symbols?1?${mam_cc_DEBUG} -D_BLD_DEBUG?${mam_cc_OPTIMIZE}?}
-setv CCLDFLAGS ${-strip-symbols?1?${mam_cc_LD_STRIP}??}
 setv COTEMP $$
-setv CPIO cpio
-setv CPIOFLAGS
-setv CPP "${CC} -E"
-setv F77 f77
-setv HOSTCC ${CC}
 setv IFFEFLAGS
-setv IGNORE
-setv LD ld
 setv LDFLAGS ""
-setv LEX lex
-setv LEXFLAGS
-setv LPR lpr
-setv LPRFLAGS
-setv M4FLAGS
-setv NMAKE nmake
-setv NMAKEFLAGS
-setv PR pr
-setv PRFLAGS
-setv SHELL /bin/sh
-setv SILENT
-setv TAR tar
-setv YACC yacc
-setv YACCFLAGS -d
 make ${PACKAGEROOT}/lib/package/ast.lic
 done ${PACKAGEROOT}/lib/package/ast.lic
 make install
diff --git a/src/lib/libdll/Mamfile b/src/lib/libdll/Mamfile
index d2248dcc4..0ef420e96 100644
--- a/src/lib/libdll/Mamfile
+++ b/src/lib/libdll/Mamfile
@@ -10,41 +10,15 @@ note * http://web.archive.org/web/20041227143022/http://www2.research.att.com/~g
 note *
 setv INSTALLROOT ../../..
 setv PACKAGE_ast_INCLUDE ${INSTALLROOT}/include/ast
-setv PACKAGE_ast_LIB ${INSTALLROOT}/lib
 setv PACKAGEROOT ../../../../..
 setv AR ${mam_cc_AR} ${mam_cc_AR_ARFLAGS}
-setv ARFLAGS rc
-setv AS as
-setv ASFLAGS
 setv CC cc
 setv mam_cc_FLAGS ${mam_cc_DLL}
 setv KSH_RELFLAGS
 setv CCFLAGS ${-debug-symbols?1?${mam_cc_DEBUG} -D_BLD_DEBUG?${mam_cc_OPTIMIZE}?}
-setv CCLDFLAGS ${-strip-symbols?1?${mam_cc_LD_STRIP}??}
 setv COTEMP $$
-setv CPIO cpio
-setv CPIOFLAGS
-setv CPP "${CC} -E"
-setv F77 f77
-setv HOSTCC ${CC}
 setv IFFEFLAGS
-setv IGNORE
-setv LD ld
 setv LDFLAGS
-setv LEX lex
-setv LEXFLAGS
-setv LPR lpr
-setv LPRFLAGS
-setv M4FLAGS
-setv NMAKE nmake
-setv NMAKEFLAGS
-setv PR pr
-setv PRFLAGS
-setv SHELL /bin/sh
-setv SILENT
-setv TAR tar
-setv YACC yacc
-setv YACCFLAGS -d
 make ${PACKAGEROOT}/lib/package/ast.lic
 done ${PACKAGEROOT}/lib/package/ast.lic
 make install
diff --git a/src/lib/libsum/Mamfile b/src/lib/libsum/Mamfile
index ec85551ae..6304ee499 100644
--- a/src/lib/libsum/Mamfile
+++ b/src/lib/libsum/Mamfile
@@ -10,41 +10,15 @@ note * http://web.archive.org/web/20041227143022/http://www2.research.att.com/~g
 note *
 setv INSTALLROOT ../../..
 setv PACKAGE_ast_INCLUDE ${INSTALLROOT}/include/ast
-setv PACKAGE_ast_LIB ${INSTALLROOT}/lib
 setv PACKAGEROOT ../../../../..
 setv AR ${mam_cc_AR} ${mam_cc_AR_ARFLAGS}
-setv ARFLAGS rc
-setv AS as
-setv ASFLAGS
 setv CC cc
 setv mam_cc_FLAGS ${mam_cc_PIC}
 setv KSH_RELFLAGS
 setv CCFLAGS ${-debug-symbols?1?${mam_cc_DEBUG} -D_BLD_DEBUG?${mam_cc_OPTIMIZE}?}
-setv CCLDFLAGS ${-strip-symbols?1?${mam_cc_LD_STRIP}??}
 setv COTEMP $$
-setv CPIO cpio
-setv CPIOFLAGS
-setv CPP "${CC} -E"
-setv F77 f77
-setv HOSTCC ${CC}
 setv IFFEFLAGS
-setv IGNORE
-setv LD ld
 setv LDFLAGS
-setv LEX lex
-setv LEXFLAGS
-setv LPR lpr
-setv LPRFLAGS
-setv M4FLAGS
-setv NMAKE nmake
-setv NMAKEFLAGS
-setv PR pr
-setv PRFLAGS
-setv SHELL /bin/sh
-setv SILENT
-setv TAR tar
-setv YACC yacc
-setv YACCFLAGS -d
 make ${PACKAGEROOT}/lib/package/ast.lic
 done ${PACKAGEROOT}/lib/package/ast.lic
 make install