can anyone tell me what this code is trying to-do

It's trying to confuse you. Looks like it succeeded.

Running it though B::Deparse gives the following, which might be a bit clearer.

BEGIN { $/ = "\n"; $\ = "\n"; }
LINE: while (defined($_ = <ARGV>)) {
    chomp $_;
    {
        ++$_;
        --$_;
        $_ ||= 4;
        if ($_ >> 2 or $_ << 2 > 12) {
            $_ = 'Vainyvq ragel';
            &{$F[0];};
            last;
        }
        &t;
        $0 -= $_;
        $_ = 'Lbh jva';
        die &{$F[0];} if not $0 - 1;
        $0 -= $0 % 2 ? ($0 > 2 ? 2 : 1) : ($0 <= 5 ? ($0 > 2 ? 3 : 1) 
+: (rand > 0.5 ? 1 : 3));
        $_ = 'V jva';
        die &{$F[0];} if not $0 - 1 > 1;
    }
    &v;
}

[download]
--
<http://dave.org.uk>

"The first rule of Perl club is you do not talk about Perl club."
-- Chip Salzenberg

In reply to Re: Code Question by davorg
in thread Code Question by Anonymous Monk

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.