canon.pl

use strict;
use warnings;

sub canonpath {
    my $path = shift;
    my @ret = ();
    for my $tok (split(/\/+/, $path)) {
         next if $tok eq '.';
         if ($tok eq '..') {
             pop @ret;
             next;
         }
         push @ret, $tok if $tok;
    }
    '/' . join '/', @ret
}

warn canonpath('/var/tmp/./foo/../bar/..');