use strict;
use warnings;

use Test::More tests => 1;

my %read2seq = (
    foo => [123, 123],
    bar => [456, 789]
);

my @want = ('foo');

my @samevals = grep { $read2seq{$_}->[0] eq $read2seq{$_}->[1] } keys %read2seq;

is_deeply \@samevals, \@want;