CGI Perl

#!/usr/bin/perl -T
use strict;
use URI::Escape;
use CGI qw/:standard/;
my $unsafestring = "\$5/[3454]/this is a windows filename.asp";
my $safestring = uri_escape($unsafestring);
my $unescstring = uri_unescape($safestring);
print header,
      start_html("start"),
      p("unsafe URL: $unsafestring\n"),
      p("url_escape(): $safestring\n"),
      p("$unescstring: $unescstring\n"),
end_html;
exit;