...
...
my $getpid = -1;

while ( my @ready = $sel->can_read ) {
...
...

	# If end-of-file (STDERR or STDOUT)
	if ( eof ($fh) ) {
		# Get pid
		my $getpid	= waitpid($pid, WNOHANG);
		$retcode	= $? / 256 if ( $getpid == $pid );
	}	
}

print "Exit code: $retcode\n";
...
...