use Parallel::ForkManager qw( )

use constant MAX_PROCESSES => 3;

my $pm = Parallel::ForkManager->new(MAX_PROCESSES);
foreach $data (@array) {
   # Forks and returns the pid for the child:
   my $pid = $pm->start and next; 

   ... do some work with $data in the child process ...

   $pm->finish; # Terminates the child process
}