BEGIN {
    # decide at compile time how to check for a process' memory size.
    if (($Config{'osname'} eq 'solaris') &&
     ($Config{'osvers'} >= 2.6)) {
    $HOW_BIG_IS_IT = \&solaris_2_6_size_check;
    } elsif ($Config{'osname'} eq 'linux') {
    $HOW_BIG_IS_IT = \&linux_size_check;
    } elsif ($Config{'osname'} =~ /(bsd|aix)/i) {
    # will getrusage work on all BSDs?  I should hope so.
    if (eval("require BSD::Resource;")) {
        $HOW_BIG_IS_IT = \&bsd_size_check;
    } else {
        die "you must install BSD::Resource for Apache::SizeLimit to w
+ork on your platform.";
    }
    } else {
    die "Apache::SizeLimit not implemented on your platform.";
    }
}
[download]

Right. There's no portable way to do it. Apache::GTopLimit uses a library from the Gnome project to abstract it, but it's harder to install because of that.