Not sure what you exactly want, but this might help you a bit further:

#!/usr/bin/perl
use Cwd;

open(FILE, "<dup01032004.txt");

while (<FILE>) {

$hash{$.} = $_;

}

close(FILE);

foreach (keys %hash) {
        my ($num) = $hash{$_} =~ m/(.*)?\..*/;
        if (-d $num) {
                # ah! the folder exists!
                print("The folder $num exists! so make your killerapp
                       do the work!!!\n");
                chdir $num or die("Cannot change to directory\n");
                print "Current folder = " . getcwd() . "\n";

                #Now do your stuff in this folder here!

                chdir ".." or die("Cannot go back...\n");
                print "Current folder = " . getcwd() . "\n";
        }

}
[download]