You may have copied part of it slightly wrong. When I used a local variable and a named string in open2, it really was important that I did so.

If you read the documentation for IPC::Open2 you'll see that I'm trying to get Perl to dup the filehandle directly. That is important because a close will fail there because your first process already has unread data that it wants PIPE to read before it exits.

If that isn't the problem, then you should make your own private copy of IPC::Open3, be sure that you are loading that version (eg with a use lib), and then start inserting debugging statements to figure out where and when it is doing the close.

Also I will warn you. Depending on how app1 is coded, figuring out how to kill it might not work for you. After all when it forks, its kids might be talking to their STDOUT, which means that the second process in the pipeline is still being talked to. And if the kids ignore the signal when dad dies...

Another thing to re-check. Does app1 really talk on STDOUT? If it talks on STDERR, or changes its behaviour when it finds itself not on a terminal, it could be very confusing. The output of app1 arguments here | cat 2> /dev/null at the shell might be revealing. (That calls it with output hooked to a pipe, and hides STDERR.)