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

my @values = qw( 11673326 11673329 11673325 11673330 11673321 11673335
+ );

my @sorted = sort { $a <=> $b } @values;
sub next_higher {
    my ($from) = @_;
    for (@sorted) {
        return $_ if $_ > $from;
    }
    return
}

use Test::More;

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

Or just remember the closest number so far (and handle the case where it's not yet defined):

#!/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_f
+ar);
    }
    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
[download]

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
[download]