Git: Find duplicate blobs (files) in this tree

#!/usr/bin/perl

# usage: git ls-tree -r HEAD | $PROGRAM_NAME

use strict;
use warnings;

my $sha1_path = {};

while (my $line = <STDIN>) {
    chomp $line;

    if ($line =~ m{ A d+ s+ w+ s+ (w+) s+ (S+) z }xms) {
        my $sha1 = $1;
        my $path = $2;

        push @{$sha1_path->{$sha1}}, $path;
    }
}

foreach my $sha1 (keys %$sha1_path) {
    if (scalar @{$sha1_path->{$sha1}} > 1) {
        foreach my $path (@{$sha1_path->{$sha1}}) {
            print "$sha1  $pathn";
        }

        print '-' x 40, "n";
    }
}

git ls-tree -r HEAD |
    sort -t ' ' -k 3 |
    perl -ne '$1 && / $1t/ && print "e[0;31m" ; / ([0-9a-f]{40})t/; print "$_e[0m"'

git ls-tree -r HEAD