This dies with a message from the forked pid. Although the die message on the line gets lost. I can't seem to figure out why your script dosn't work? I did find if you put a print statement BEFORE your next open statement, your script will die at the right line. Without the print, it stays alive and tries the next open. ????

#!/usr/bin/perl
use warnings;
use strict;
use IPC::Open2;

my $cmd = '/no/such/command';
my($out,$in);
open2($out, $in, $cmd) || die("I thought script should die here: $!");

print $in "the_string\n" || die ("print die here no fork: $!");
open(my $pipe, "$cmd|") || die("But it dies only here: $!");
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It gives the error:

open2: exec of /no/such/command failed at ./655683.pl line 10