Wasn't this the classic?

#!/usr/bin/env perl

use POSIX qw(setsid);

print daemonize();

sub daemonize {

   my $child = fork;

   if ( definded ($child) ) {
       exit 0 ;
   } else {
       die qq(I really can't...!\n);
   }

   setsid();

   open( STDIN, "</dev/null" );
   open( STOUT, ">/dev/null" );
   open( STDIN, ">&STDOUT" );

   chdir '/';

   umask(0);

   ENV{PATH}=q(/what/you/like); 

   return $$;
}
[download]

Please see also Parallel::ForkManager.

Regards, Karl