If you want to sort an array naturally (the way a human would) you can use Perl's sort() function, but use a custom sort method:

my @input  = qw(foo foo250 foo12 foo23 bar999 bar7 bar17 bar99 18);
my @sorted = sort { natural(); } @input;

print join(", ", @sorted);

sub natural {
    # Separate the word and numeric parts
    my ($word_a, $num_a) = $a =~ /(.*?)(\d+|$)/;
    my ($word_b, $num_b) = $b =~ /(.*?)(\d+|$)/;

    #print "$a / $b: $word_a, $num_a, $word_b, $num_b\n";

    # If the words are diff it's an alpha sort on the words
    if ($word_a ne $word_b) {
        return $word_a cmp $word_b;
    # Words are the same, numeric sort the number part
    } else {
        return ($num_a || 0) <=> ($num_b || 0);
    }
}

See also: Natural Sort