use IO::Select;

my %pid;
my $s = IO::Select->new();

for (qw(proc1 proc2 proc3)) {
    my $pid = open my $fh, "-|", $_
        or warn "Could not fork&open '$_': $!"
        and next;

    $pid{$fh} = [ $pid, $_ ];
    $s->add($fh);
}

while (my @ready = $s->can_read) {
    for my $fh (@ready) {
        if (eof $fh) {
            delete $pid{$fh};
            $s->remove($fh);
            next;
        }

        my $line = <$fh>;
        if ($line =~ /desktop/) {
            chomp $line;
            print "Found 'desktop' in '$line' from $pid{$fh}[1]\n";
            kill 15, map {$_->[0]} values %pid;
        }
    }
}