Your CGI-params get html_unescaped when retrieving the value, i.e. the string %00 is converted to a _real_ ASCII NUL ("\0" in perl). Match that. 
#!/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

[download]

--shmem 

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}

In reply to Re: How to specify a Null char in a match operation by shmem
in thread How to specify a Null char in a match operation by Nik

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