#!/usr/bin/perl -w
use strict;
use POSIX;

# incomplete example, tailor to you needs

$| = 1;

my $pid = fork;
my $result;
if ($pid) {
        my $kid;
        print "Please Wait...<br>\n";
        do {
                sleep 2;
                print "\0";
                $kid = waitpid(-1, &WNOHANG);
                if ($kid > 0) {
                        $result = $? >> 8;
                }
        } until ($kid == -1);
} else {
        if (defined $pid) {
                exec("./long_running_prog");
                CORE::exit 1;
        } else {
                print "Failed to fork!<br>";
                $result = 1;
        }
}

if (not $result) {
        print "Run successful<br>\n";
} else {
        print "Run Failed. Error($result)<br>\n";
}