(perl-font-lock-keywords): Add a `(... . 1)' to the

(perl-font-lock-keywords): Add a `(... . 1)' to the
first element of the list.
(font-lock-hack-keywords, font-lock-unfontify-region)
(font-lock-fontify-region): Bind buffer-read-only to nil,
and don't alter buffer-modified-p.
(font-lock-fontify-region): Use comment-start-skip, not comment-start.

(font-lock-function-name-face): defvar renamed.
(font-lock-hack-keywords): Evaluate face specs from keyword list.