#!/usr/bin/perl -wT

package Parent;
1;

package Child;
@ISA = qw(Parent);
1;

package main;

%ENV = ();

use strict;

our $isa;

$|++;
print "Type in something: ";
$isa = <STDIN>;

$isa = "/bin/ls";
print "(qx)  ", (eval { qx($isa); 1 } ? "Untainted" : "Tainted"), "\n";

$isa = "Child";
print "(isa) ", ($isa->isa("Parent") ? "Untainted" : "Tainted"), "\n";