+GNUM4=
+for prog in $M4 gm4 gnum4 m4; do
+ # continue if $prog generates error (e.g. does not exist)
+ ( $prog --version ) < /dev/null > /dev/null 2>&1
+ if test $? -ne 0 ; then continue; fi
+
+ # /dev/null input prevents a hang of the script for some m4 compilers (e.g. on FreeBSD)
+ case `$prog --version < /dev/null 2>&1` in
+ *GNU*) GNUM4=$prog
+ break ;;
+ esac