You mentioned twice that there's a benchmark discrepancy between the while loop and the readdir loop. While you're in a benchmarking mood, if you're so inclined, please show us the results of the three forms:

while ($eachfile = <*.txt>)
    { ... }
[download]

@files = <*.txt>;
foreach (@files)
    { ... }
[download]

opendir(DIR, ...);
while (defined ($eachfile = readdir(DIR) ))
    { next if not /\.txt$/; ... }
[download]

Of course, there's platform differences to consider, too. Some filesystems bog down worse than others with long directories.

If you're bored, check that @files = <*.txt> is really just as fast as @files = glob("*.txt"), too.