Much easier as "forked open"

#!/usr/bin/perl

# http://perlmonks.org/?node_id=1148787

use strict;
use warnings;

my $total = 0.0;
my @waitlist = qw(0 200 400 800 1000);
my @fhs;

foreach my $item (@waitlist)
  {   
  if( open my $fh, '-|' )
    {   
    push @fhs, $fh;
    }   
  else
    {   
    my $h = 1.0 / 1200.0;
    my $sum = 0.0;
    for my $i ($item .. $item + 200 )
      {         
      my $x = $h * ($i - 0.5);
      $sum += 4.0 / (1.0 + $x*$x);
      }   
    my $ret=$sum * $h; 
    print $ret;
    #warn "$item exiting\n";
    exit; 
    }   
  }

for my $fh ( @fhs )
  {
  $total += (<$fh> + 0.0);
  print "$total\n";
  close $fh;
  }
   
print " $total\n";
print "All done!\n";
[download]

ninja'd...nevermind

#!/usr/bin/perl -w
use feature 'say';
use IO::Handle;

my $total=0.0;
@waitlist = qw(0 200 400 800 1000);

foreach $item (@waitlist) {
  pipe(*{$item},RETHAND);
  *{$item}->autoflush(1);
  RETHAND->autoflush(1);
  unless (my $pid = fork()) {
    my $h = 1.0 /1200.0;
    my $sum = 0.0;
    for (my $i = $item; $i < ($item+200); $i++){        
    my $x = $h * ($i - 0.5);
    $sum += 4.0 / (1.0 + $x*$x);
    }
    my $ret=$sum*$h;
    print RETHAND "$ret";
    exit; 
  }else{
    close RETHAND
  }
}

foreach $item (@waitlist) {
  $response = <$item>;
  $total+= ($response+0.0);
  print "$total\n";
}  


1 while (wait() != -1);
print " $total\n";
print "All done!\n";
[download]

why do you indent your code so creatively???

Right back atchya!

#!/usr/bin/perl
# http://perlmonks.org/?node_id=1148787
use strict;
use warnings;

my $total = 0.0;
my @waitlist = qw(0 200 400 800 1000);
my @fhs;

foreach my $item (@waitlist) {
    if( open my $fh, '-|' ) {
        push @fhs, $fh;
    }
    else {
        my $h = 1.0 / 1200.0;
        my $sum = 0.0;
        for my $i ($item .. $item + 200 ) {
            my $x = $h * ($i - 0.5);
            $sum += 4.0 / (1.0 + $x*$x);
        }
        my $ret=$sum * $h;
        print $ret;
        #warn "$item exiting\n";
        exit;
    }
}

for my $fh ( @fhs ) {
    $total += (<$fh> + 0.0);
    print "$total\n";
    close $fh;
}
   
print " $total\n";
print "All done!\n";
[download]

Much nicer! :)

---

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority". I knew I was on the right track :)

In the absence of evidence, opinion is indistinguishable from prejudice.

Indeed, much better, I also prefer The One True Way (aka perltidy's default settings). BTW, that was a different anonymonk :)