#! perl -slw
use strict;
use threads;
use threads::shared;

our $N //= 12;
our $I //= 0;

my $cmd = qq[$^X -E"\$|++; sleep $N; print 'Kid got ', scalar <STDIN> if $I; sleep 2;say 'Kid done'"];

my $timeout = time() + 10;
my $inInputState :shared = 0;

my $pid = open CMD, '|-', $cmd or die $!;
my $old = select CMD; $|++; select $old;
my $timedOut = 0;

async {
    $inInputState = 1 if printf CMD " \b"x2048;
}->detach;

Win32::Sleep 10 until !kill 0, $pid
    or $timedOut = time() > $timeout
    or $inInputState
;

if( $timedOut ) {
    print "Command timed out";
    kill 3, $pid;
}
if( $inInputState ) {
    print "Child waiting for input";
    print CMD 'hello';
}
else {
    print "Kid never entered input state";
}

print 'Parent done';