hartmann@ds0050:~/learning/forkArena> cat parallelize_em_demo.pl
#!/usr/bin/perl
use strict;
use warnings;
use Carp qw(confess);

my @commands = map {
  "touch $_; ls -l $_; sleep 2";
} qw(a b c d e);

my ( $time_start, $time_elapsed_serial, $time_elapsed_parallel);

$time_start=time();
#does first, waits two seconds, does the second, waits two seconds, etc. (should take about ten seconds)
for my $bash_command ( @commands  ) {
  run_bash_command($bash_command);
}
$time_elapsed_serial = time()-$time_start;
print "\ntime elapsed serial: $time_elapsed_serial\n\n";

#does commands in parallel. (should take about two seconds)
my $parallel_running_command = parallelize_bash_commands([@commands]);

$time_start = time();
run_bash_command($parallel_running_command);
$time_elapsed_parallel = time()-$time_start;
print "\ntime elapsed parallel: $time_elapsed_parallel\n\n";

sub run_bash_command {
  my $command = shift or die "no command";
  print "$command\n";
  print `$command`;
}

sub parallelize_bash_commands {
  my $commands = shift or confess "no commands";
  ref($commands) eq 'ARRAY' or confess "not an array";

  my $parallel_running_command = "";
  for my $command ( @$commands  ) {
    $parallel_running_command .= "( ( $command ) & );";
  }
  return $parallel_running_command;
}