This is exactly what I would suggest, with the added comment that I have used this approach with excellent results. 

use Parallel::ForkManager;
$pm = Parallel::ForkManager->new(2);

foreach my $input_file (@files) {
    my $pid = $pm->start and next; 

    system("shell_script < $input_file");

    $pm->finish; # Terminates the child process
}

[download]
Your actual code may vary, depending on requirements

This works well on both Windows and UNIX, and as long as the OS manages the SMP tasks correctly, your threads will use both CPUs (one thread will only use one CPU, obviously) if needed.

Updates:

<-radiant.matrix->
A collection of thoughts and links from the minds of geeks
The Code that can be seen is not the true Code
"In any sufficiently large group of people, most are idiots" - Kaa's Law

In reply to Re^2: Is fork() my answer to using dual-cpu? by radiantmatrix
in thread Is fork() my answer to using dual-cpu? by axl163

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.