Here are a few links to documentation on the subject...

POE Central
SourceForge page for POE
A Beginner's Introduction to POE

Good luck! (No, I'm not a POE expert, but I certainly want to be one one day...)

Cheers,
Richard

Go for Event!

It's ugly, unfactor'd, but works.

use Event;
use IO::File;

my $f = IO::File->new('for t in 1 2 3 4;do echo one $t; sleep 4;done; 
+|');
my $g = IO::File->new('for t in 1 2 3 4;do echo two $t; sleep 4;done; 
+|');
my $h = IO::File->new('for t in 1 2 3 4;do echo three $t; sleep 4;done
+; |');
my (@f,@g,@h);

my $done;

sub newIO {
  my ($f,$fr) = @_;
  Event->io(
    fd => $f,
    poll => 're',
    cb => sub {
      my $e = $_[0];
      my $w = $e->w;
      my $fd = $w->fd;
      if ($fd->eof) {
          $pending--;
          $w->cancel;
          return;
      }
      my $line = <$fd>;
      push @{$fr}, $line;
      },
  );
  $pending++;
}
Event->idle(
    min => 1, max => 2,
    cb => sub {
        print "last one: $f[-1]";
        print "last two: $g[-1]";
        print "last three: $h[-1]";
        Event::unloop if ($pending == 0);
    },
);
newIO($f,\@f);
newIO($g,\@g);
newIO($h,\@h);
Event::loop;
print @f;
print @g;
print @h;
[download]

Gives:

last one: one 1
last two: two 1
last three: three 1
last one: one 1
last two: two 1
last three: three 1
last one: one 1
last two: two 1
last three: three 1
last one: one 2
last two: two 2
last three: three 2
last one: one 2
last two: two 2
last three: three 2
last one: one 2
last two: two 2
last three: three 2
last one: one 2
last two: two 2
last three: three 2
last one: one 3
last two: two 3
last three: three 3
last one: one 3
last two: two 3
last three: three 3
last one: one 3
last two: two 3
last three: three 3
last one: one 3
last two: two 3
last three: three 3
last one: one 4
last two: two 4
last three: three 4
last one: one 4
last two: two 4
last three: three 4
last one: one 4
last two: two 4
last three: three 4
last one: one 4
last two: two 4
last three: three 4
last one: one 4
last two: two 4
last three: three 4
one 1
one 2
one 3
one 4
two 1
two 2
two 3
two 4
three 1
three 2
three 3
three 4

I heard a talk about them at the German Perl Workshop, very impressive.

:
 perl umstat.pl &
 perl cpustat.pl &
[download]

sub BothStat {
          $cpuoutput_time = time;
          $vmoutput_time = time;
          open (VMOUT, "$vmstat |");
          open (CPUOUT, "$cpustat |");
          @cpuoutput = <CPUOUT>;
          $vmoutput = <VMOUT>;
          close (CPUOUT);
          close (VMOUT);
}
[download]

1. sockets
2. files with flock()
3. pipes

open(VMSTAT, "vmstat |");
open(CPUSTAT, "cpustat |");
open(...
[download]

Select is a bit cumbersome to use (good example in the Camel book). Perhaps you get the parallelism you need just by starting the commands in parallel. Then just read from them one at a time. Do you need to read just one line from each command, or are you expecting multiple lines?

-- Dino

Thank you all for your replies. I am going to look at POE and Coroutine in the future, because it looks like they would both solve this problem. However, I've found a alternative to running all of these commands that serves me better.

I'm going to use the Sun::Solaris::Kstat module to pull all of these stats, and update at the same time. So it'll take a matter of nanoseconds to get all the stats I need every five seconds instead of having to wait on shell commands.

It'll be pretty sweet when its done. Look for it on freshmeat!