Nobody mentioned the Shell module that comes standard with Perl. It does some hackery with AUTOLOAD to see if any undefined routines are shell commands. Here are some examples of what it can do quoted from the documentation

    #!/usr/bin/perl

    use Shell;

    $foo = echo("howdy", "<funny>", "world");
    print $foo;

    $passwd = cat("</etc/passwd");
    print $passwd;

    sub ps;
    print ps -ww;

    cp("/etc/passwd", "/tmp/passwd");
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HTH