#!/usr/bin/perl

package TieTest;

sub TIEHANDLE { return bless {}, shift }
sub OPEN      { open my $fh, $_[1], $_[2]; $_[0]->{fh} = $fh; }
sub READ      { warn "...tied read\n"; read $_[0]->{fh}, $_[1], $_[2], $_[3]; }
sub SEEK      { seek $_[0]->{fh}, $_[1], $_[2]; }

package main;

use strict;
use warnings;
use Digest::MD5;
use Digest::Perl::MD5;

open FH_PLAIN, '<', $ARGV[0];

#open FH_TIED,  '<', $ARGV[1]; # try uncommenting this
tie(*FH_TIED, 'TieTest');
open FH_TIED, '<', $ARGV[0];

my %handles = (PLAIN => \*FH_PLAIN, TIED => \*FH_TIED);
for my $title (qw/PLAIN TIED/) {

    my $fh = $handles{$title};
    for my $class (qw/Digest::Perl::MD5 Digest::MD5/) {

        my $sum = $class->new->addfile($fh)->hexdigest;
        printf "%-7s%-19s%-32s\n", $title, $class, $sum;
        seek $fh, 0, 0;
    
    }

}