$ echo 123123 | wr2
123123

##</code><code>##

#!/usr/bin/perl

use warnings;
use strict;

use IPC::Run qw(start pump finish timeout);

#my @cat = qw(/bin/cat);
my @cat = qw(/home/cwood/bin/wr2);

my ($in, $out, $err);

my $h = start \@cat, \$in, \$out, \$err, timeout(10);

$in .= "some input\n";
pump $h until $out =~ /input\n/g;

$in .= "some more input\n";
pump $h until $out =~ /\G.*more input\n/;

$in .= "some final input\n";
finish $h or die "cat returned $?";

warn $err if $err;
print $out;    ## All of cat's output

##</code><code>##

#!/usr/bin/perl

use warnings;
use strict;

while (<STDIN>) {
    print;
}