#!/usr/bin/perl -T --
use strict;
use warnings;

use Scalar::Util qw' tainted ';

{
    use re qw' taint ';
    print '$^X tainted ', tainted($^X), "\n";
    print '$1 tainted ', tainted($1), "\n";
    print '"$1" tainted ', tainted("$1"), "\n";
    print '($^X=~/(.)/) tainted ', tainted($^X=~/(.)/), "\n";
    {print '(my($x)=$^X=~/(.)/) tainted ', tainted(my($x)=$^X=~/(.)/), "\n";}
    print '$1 tainted ', tainted($1), "\n";
    print '"$1" tainted ', tainted("$1"), "\n";
    {print '(my($x)=$^X=~s/(.)/$1/) tainted ', tainted(my($x)=$^X=~s/(.)/$1/), "\n";}
    print '$1 tainted ', tainted($1), "\n";
    print '"$1" tainted ', tainted("$1"), "\n";
}
print "\n", '='x33,"\n";
{
    no re qw' taint ';
    print '$^X tainted ', tainted($^X), "\n";
    print '$1 tainted ', tainted($1), "\n";
    print '"$1" tainted ', tainted("$1"), "\n";
    print '($^X=~/(.)/) tainted ', tainted($^X=~/(.)/), "\n";
    {print '(my($x)=$^X=~/(.)/) tainted ', tainted(my($x)=$^X=~/(.)/), "\n";}
    print '$1 tainted ', tainted($1), "\n";
    print '"$1" tainted ', tainted("$1"), "\n";
    {print '(my($x)=$^X=~s/(.)/$1/) tainted ', tainted(my($x)=$^X=~s/(.)/$1/), "\n";}
    print '$1 tainted ', tainted($1), "\n";
    print '"$1" tainted ', tainted("$1"), "\n";
}
__END__

$ perl -T re.taint.pl
$^X tainted 1
$1 tainted 0
Use of uninitialized value $1 in string at re.taint.pl line 11.
"$1" tainted 0
($^X=~/(.)/) tainted 0
(my($x)=$^X=~/(.)/) tainted 1
$1 tainted 0
"$1" tainted 1
(my($x)=$^X=~s/(.)/$1/) tainted 1
$1 tainted 0
"$1" tainted 1

=================================
$^X tainted 1
$1 tainted 1
Use of uninitialized value $1 in string at re.taint.pl line 25.
"$1" tainted 1
($^X=~/(.)/) tainted 0
(my($x)=$^X=~/(.)/) tainted 0
$1 tainted 1
"$1" tainted 0
(my($x)=$^X=~s/(.)/$1/) tainted 0
$1 tainted 0
"$1" tainted 0