Does it have to be IPC? If so, you need to make a pipe to read from each of the child processes. It would be easiest to use IPC::Open2. Or you can just use a simple piped form of open. Here is a way to do it for just one child, loop it 3 times, for your needs. If you need them simultaneous, put the CHILD filehandles in a hash, and use IO::Select to read them.

#!/usr/bin/perl
use strict;
use warnings;

my $pid = open(CHILD, "-|");

if ($pid)
{
   # parent 
   print "parent got:\n";
   print while(<CHILD>);
   close CHILD; # this waits on child 
}
elsif ($pid == 0)
{
   # child 
   print "kid here!\n";
   exec '/bin/date' or die "Can't exec date $!\n";
}
else
{
   die "fork error: $!\n";
}
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