#!/usr/bin/perl -w
use CGI;
use strict;

my $q = new CGI;
print $q->header;
print $q->start_html;
my $p = $q->param('foo');

print $p =~ s/\0/�/g ? "$p - null char detected\n" : "$p fine.\n";

print $q->end_html;
__END__
call e.g. with http://localhost/cgi-bin/foo.pl?foo=foo%00bar