Using the /e modifier of a regex for such uses is just plain wrong. It looks more like you are obfuscating code than writing it. Much better written in a form such as the following (mine will also do reverse conversions -- F to C): 

#!/usr/bin/perl -w

use strict;

while (<DATA>) {
    chomp;
    next unless (m!\A([+-]?(?:\d*\.)?\d+)([CF])\z!);

    print "$_ is ", (
        $2 eq 'C' ?
            $1 * 9 / 5 + 32 . 'F' :
            ($1 - 32) * 5 / 9 . 'C'
    ), $/;
}

__END__
12C
13C
14C
15C
-40C
+32C
.5C
15.8C
60.44F
55.4F
-.7F

[download]

In reply to Re^3: Celsius to Fahrenheit using s/// by saskaqueer
in thread Celsius to Fahrenheit using s/// by tphyahoo

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.