Sequentially?

   use strict;
   use warnings;
   foreach (@ARGV) {
      &process($_);
   }
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In parallel?

   use strict;
   use warnings;
   foreach (@ARGV) {
      die "Fork failed: $!\n" unless defined (my $pid = fork);
      exit &process($_) unless $pid;
   }
   1 until -1 == wait;
   ...
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Restrained parallel?

   use strict;
   use warnings;
   my $max = 4;
   my $c   = 0;
   foreach (@ARGV) {
      wait unless ++$c <= $max;
      die "Fork failed: $!\n" unless defined (my $pid = fork);
      exit &process($_) unless $pid;
   }
   1 until -1 == wait;
   ...
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I leave the process routine and appropriate error checking to you.