use warnings;
use strict;

use Proc::Background;

my @cmd = qw(perl sleep.pl);

my $proc = Proc::Background->new(@cmd);
my $pid = $proc->pid;

print "*** $pid ***\n";

##</code><code>##

~/scratch$ perl proc.pl 
*** 3489 ***

~/scratch$ ps ax | grep sleep
 3489 pts/1    S      0:00 perl sleep.pl