use strict;
use warnings;
use diagnostics;
use Parallel::ForkManager;

my $pm = new Parallel::ForkManager(2);

# This works
pm->run_on_finish( sub { print "Hello!\n"; } );

# This doesn't
#sub hello { print "Hello!\n"; }
#$pm->run_on_finish( &hello );

foreach my $child ( 0 .. 4 ) {
    my $pid = $pm->start and next;
	
    $pm->finish;
}

$pm->wait_all_children;