I guess you might be storing the list of contents of a directory in a flat file, and want to check if the current contents differ from the stored record.

In that case I would build a hash of the lines of the file like so:

%files = map { tr/\015\012//d; ($_,1); } (<FILE>);

Where FILE is an already open filehandle.
Then I would loop over the directory like so (where DIR comes from opendir):

while (defined($_ = readdir(DIR))) {
    next if /^\.\.?$/;
    unless (delete $files{$_}) {
        print "New: $_\n";
    }
}
[download]

Reporting things that weren't in the file and removing the others from the hash.
And finally reporting thing from the file that are no longer in the directory:

for (keys %files) {
    print "Gone: $_\n";
}
[download]

Of course if you are not asking for that, then your question needs clarification.

2001-03-04 Edit by Corion : Removed an erroneous <CODE> tag