Note: If you don't do this, Windows will do it for you, but it's better to explicitly close the handle, especially if running from Rexx Programmer Center (where you could otherwise get an error about another mailslot already having the same name if you run the script a second time). It's best to put this into a FINALLY section so that it is always done.
/* Close the mailslot */ IF EXISTS(handle) THEN CloseHandle(handle)