Trying the reload button failed with:
Can't open perl script "./guido.pl": Datei oder
Verzeichnis nicht gefunden (File or directory not
It seems that the current directory changed while
guido. I see two solutions: make the path of guido.pl
(there is a method rel2abs in File::Spec), or use the
function which makes sure that after leaving the block
user will still stay in the same directory.