use POSIX ":sys_wait_h"; my @tasks = (1..398); my %kids; { while (@tasks and keys %kids < 5) { $kids{fork_a_task(shift @tasks)} = "active"; } { my $pid = waitpid(-1, 0); if ($pid == -1) { %kids = (); } else { delete $kids{$pid}; } } redo if @tasks or %kids; } sub fork_a_task { my $i = shift; my $pid = fork; return $pid if $pid; unless (defined $pid) { warn "cannot fork: $!"; return 0; } ## do stuff for task $i goes here... exit 0; }