The following patch clarifies what ord("") does in pod/perlfunc.pod.
From the current documentation, it's not documented what it does, and one
could guess several different things: returns zero, returns undef, returns
zero with a warning, returns undef with a warning, dies. (There's precedent
for dying: some BASIC implementations give an error if you ask for ASC("")
-- here ASC is their equivalent of our ord function.)
=item ord
Returns the numeric (the native 8-bit encoding, like ASCII or EBCDIC,
-or Unicode) value of the first character of EXPR. If EXPR is omitted,
-uses C<$_>.
+or Unicode) value of the first character of EXPR. If EXPR is an empty
+string, returns 0. If EXPR is omitted, uses C<$_>.
For the reverse, see L</chr>.
See L<perlunicode> for more about Unicode.