First suggestion: use your system's sort routine. While I think the *ix sort is better than the Windows sort, both are reliable, and quite fast.

As for sorting a list in Perl:

use strict;     # a good idea
use warnings;   # and another

my $input = 'myinput.txt';
open(my $in, "<", $input) or die "Could not open $input because $!\n";
@unsorted = <$in>;
chomp(@unsorted); # get rid of end-of-record markers
close($in);

@sorted = sort @unsorted;
[download]

will sort the @unsorted array, based on the entire string, with the output going to @sort. Note that this requires a copy of the entire file be in memory, which may be a Bad Idea. There are several tutorials, for example, here and here. And of, course, here.