The kill line, what it does is stop the WINCH event from being called again be the same event, right?

kill WINCH => $EXP -> pid if $EXP -> pid; sends the WINCH signal to the process with pid $EXP->pid. Where $EXP is an Expect object (i guess). The bottom line is that kill is sending a specified signal to a specified process. It does not stop or block a signal.