#!/usr/bin/perl
use warnings;
use strict;

my $data_start = tell *DATA;
sub next_higher {
    my ($from) = @_;
    seek *DATA, $data_start, 0;
    my $so_far;
    while (<DATA>) {
        chomp;
        $so_far = $_ if $_ > $from && (! defined $so_far || $_ < $so_far);
    }
    return $so_far
}

use Test::More;

is next_higher(11673326), 11673329;
is next_higher(11673335), undef;
is next_higher(11673321), 11673325;

__DATA__
11673326
11673329
11673325
11673330
11673321
11673335