#!/usr/bin/perl -wT
use strict;
my $foo = join('',@ARGV);
if (is_tainted($foo)) {
        print "\$foo is tainted. Attempting to launder\n";
        my $pattern = qr(^\d{3}(-|\s+)?\d{3}(-|\s+)?\d{4}$);
        $foo = untaint($foo, $pattern);
}else{
        print "\$foo is not tainted!!\n";
}
sub is_tainted {
        my $check = shift;
        return  !eval { $check++, kill 0;1;};
}
sub untaint {
        my ($foo, $pattern) = @_;
        if ($foo =~ /($pattern)/) {
                $foo = $1;
                print "\$foo has been laundered!!\n";
                return $foo;
        }else{
                print "Unable to launder \$foo\n";
                return $foo;
        }
}