That seems like a very round-about way to check for duplicate entries, and also a very very slow one (especially on filesystems that grow much slower as the number of files in a single directory increases, and many do).

How about this construct: instead of testing for and creating files, put an entry in a hash and test for that (I'm reusing your $filename variable here, except I'm not using it as a filename): 

my %seen; # declare this outside the loop

# do the following for each $filename

if ($seen{$filename}++) {
  # $filename is a duplicate
}
else {
  # never seen this before
}

[download]
Theoretically, that would run out of memory some time, but I can't imagine a situation where your file-based strategy would be any better. If you've got a Gb of RAM you should be able to store a couple of million "filenames" at least

updated: removed exists, added some comments

"What should it profit a man, if he should win a flame war, yet lose his cool?"

In reply to Re: Super fast file creation needed by Joost
in thread Super fast file creation needed by Plankton

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.