#!/usr/bin/perl -T
# This is taint.pl

use strict;
use warnings;
use IO::File;

my $fn=$ARGV[0] or die "Missing filename";
my $fh=IO::File->new();
$fh->open($fn,'w') or die "open $fn failed: $!";
$fh->print("This should not happen!");

##</code><code>##

/tmp>perl -T taint.pl /dev/null
Insecure dependency in open while running with -T switch at /usr/lib64/perl5/IO/File.pm line 184.

/tmp>perl -MCarp::Always -T taint.pl /dev/null
Insecure dependency in open while running with -T switch at /usr/lib64/perl5/IO/File.pm line 184.
        IO::File::open(IO::File=GLOB(0x1520be8), "/dev/null", "w") called at taint.pl line 10

/tmp>