Autodetect where perl is.

waste/GNUmakefile

@@ -6,3 +6,6 @@ errno:
 clean:
 	rm waste
 install: $(BINDIR)/waste
+
+%: %.pl patchperl
+	sh ./patchperl $< $@

waste/patchperl

@@ -0,0 +1,13 @@
+perl=`which perl`
+if [ $# -ne 2 ]
+then
+	echo "Usage $0 source target" >&2
+	exit 1
+fi
+if [ -z "$perl" ]
+then
+	echo "$0: cannot find perl binary" >&2
+	exit 1
+fi
+sed -e "s,@@@perl@@@,$perl," < $1 > $2
+exit 0

waste/waste.pl

@@ -1,4 +1,4 @@
-#!/usr/local/bin/perl
+#!@@@perl@@@
 
 #
 # Report wasted space.