The line 
our $data = <DATA>;

[download]
is still useless because you read to $data only the first string from __DATA__ section :)
Please modify it to 
our $data = join "", <DATA>;

[download]
IMHO it is exactly what you wanted to do:)

The worst thing about tr/// is that it can produce only character-to-character mapping. The best solution aviding this problem I found uses eval at compilation time: 

BEGIN {
our %rot = (
  'A' => 'N','B' => 'O','C' => 'P','D' => 'Q','E' => 'R','F' => 'S',
  'G' => 'T','H' => 'U','I' => 'V','J' => 'W','K' => 'X','L' => 'Y',
  'M' => 'Z','N' => 'A','O' => 'B','P' => 'C','Q' => 'D','R' => 'E',
  'S' => 'F','T' => 'G','U' => 'H','V' => 'I','W' => 'J','X' => 'K',
  'Y' => 'L','Z' => 'M','a' => 'n','b' => 'o','c' => 'p','d' => 'q',
  'e' => 'r','f' => 's','g' => 't','h' => 'u','i' => 'v','j' => 'w',
  'k' => 'x','l' => 'y','m' => 'z','n' => 'a','o' => 'b','p' => 'c',
  'q' => 'd','r' => 'e','s' => 'f','t' => 'g','u' => 'h','v' => 'i',
  'w' => 'j','x' => 'k','y' => 'l','z' => 'm',
);

my $substs = join "\n", map { "    s/$_/$rot{$_}/g;" } keys %rot;

eval <<SUB;
sub rot13s {
    local \$_ = shift;
    $substs;
    return \$_;
}
SUB

}

[download]
It is only 52 times slower than tr/// : 
          Rate  table  s///g     tr
table    448/s     --   -78%  -100%
s///g   2026/s   352%     --   -98%
tr    106383/s 23654%  5152%     --

[download]

In reply to Re: The indisputable speed of tr/// by Ieronim
in thread The indisputable speed of tr/// by radiantmatrix

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.