1 files changed, 30 insertions, 5 deletions
diff --git a/editor/ppmshadow b/editor/ppmshadow
index 2a32fca0..62cdf8b8 100755
--- a/editor/ppmshadow
+++ b/editor/ppmshadow
@@ -1,15 +1,40 @@
-#!/usr/bin/perl -w
+#!/bin/sh
 
-#                         P P M S H A D O W
+##############################################################################
+# This is essentially a Perl program.  We exec the Perl interpreter specifying
+# this same file as the Perl program and use the -x option to cause the Perl
+# interpreter to skip down to the Perl code.  The reason we do this instead of
+# just making /usr/bin/perl the script interpreter (instead of /bin/sh) is
+# that the user may have multiple Perl interpreters and the one he wants to
+# use is properly located in the PATH.  The user's choice of Perl interpreter
+# may be crucial, such as when the user also has a PERL5LIB environment
+# variable and it selects modules that work with only a certain main
+# interpreter program.
+#
+# An alternative some people use is to have /usr/bin/env as the script
+# interpreter.  We don't do that because we think the existence and
+# compatibility of /bin/sh is more reliable.
+#
+# Note that we aren't concerned about efficiency because the user who needs
+# high efficiency can use directly the programs that this program invokes.
+#
+##############################################################################
+
+exec perl -w -x -S -- "$0" "$@"
 
+#!/usr/bin/perl
+##############################################################################
+#                              ppmshadow
+##############################################################################
+#
 #            by John Walker  --  http://www.fourmilab.ch/
 #                          version = 1.2;
 #   --> with minor changes by Bryan Henderson to adapt to Netbpm.  
 #   See above web site for the real John Walker work, named pnmshadow.
-
+#
 #   Bryan Henderson later made some major style changes (use strict, etc) and
 #   eliminated most use of shells.  See Netbpm HISTORY file.
-
+#
 #   Pnmshadow is a brutal sledgehammer implemented in Perl which
 #   adds attractive shadows to images, as often seen in titles
 #   of World-Wide Web pages.  This program does not actually
@@ -20,7 +45,7 @@
 #
 #               This program is in the public domain.
 #
-#
+##############################################################################
 
 use strict;
 require 5.0;