#!/usr/bin/perl 

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

die "Usage: $0  dir1  dir2\n"
    unless ( @ARGV == 2 and -d $ARGV[0] and -d $ARGV[1] );

my %fsize;

for my $dir ( @ARGV ) {
    opendir DIR, $dir or die "$dir: $!\n";
    while ( my $fn = readdir DIR ) {
        next unless -f "$dir/$fn";
        push @{$fsize{ -s "$dir/$fn" }}, "$dir/$fn";
    }
}

my %fmd5;
my $digest = Digest::MD5->new;

for my $bc ( keys %fsize ) {
    next if scalar @{$fsize{$bc}} == 1;
    for my $fn ( @{$fsize{$bc}} ) {
        if ( open( my $fh, "<", $fn )) {
            $digest->new;
            $digest->addfile( $fh );
            push @{$fmd5{ $digest->b64digest }}, $fn;
        }
    }
}

for my $md ( keys %fmd5 ) {
    print join( " == ", @{$fmd5{$md}} )."\n" if ( scalar @{$fmd5{$md}} > 1 );
}