Installed and tested with the Parallel ForkManager version 1.03 the code is still exiting abnormally in the same section of ForkManager.pm:

Use of uninitialized value in block exit at /lib/site_perl/5.8.9/Paral
+lel/ForkManager.pm line 599.
Use of uninitialized value in block exit at /lib/site_perl/5.8.9/Paral
+lel/ForkManager.pm line 599.
Unable to create sub named "" at /lib/site_perl/5.8.9/Parallel/ForkMan
+ager.pm line 599.
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    587 sub run_on_wait {
    588   my ($s,$code, $period)=@_;
    589 
    590   $s->{on_wait}=$code;
    591   $s->{on_wait_period} = $period;
    592 }
    593 
    594 sub on_wait {
    595   my ($s)=@_;
    596 
    597   if(ref($s->{on_wait}) eq 'CODE') {
    598     $s->{on_wait}->();
    599     if (defined $s->{on_wait_period}) {
    600         local $SIG{CHLD} = sub { } if ! defined $SIG{CHLD};
    601         select undef, undef, undef, $s->{on_wait_period}
    602     };
    603   };
    604 };
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