"Manual? What's that?"


perl-mode is a thing. So is cperl-mode, a more extensive major mode for editing Perl. I’ve tried out the latter briefly for viewing a script, then did succumb to my curiosity and checked the sources after noticing weird behaviour.

;; DO NOT FORGET to read micro-docs (available from `Perl' menu)   <<<<<<
;; or as help on variables `cperl-tips', `cperl-problems',         <<<<<<
;; `cperl-praise', `cperl-speed'.                                  <<<<<<


(defvar cperl-problems 'please-ignore-this-line
  "Description of problems in CPerl mode.
Some faces will not be shown on some versions of Emacs unless you
install choose-color.el, available from

`fill-paragraph' on a comment may leave the point behind the
paragraph.  It also triggers a bug in some versions of Emacs (CPerl tries
to detect it and bulk out).

See documentation of a variable `cperl-problems-old-emaxen' for the
problems which disappear if you upgrade Emacs to a reasonably new
version (20.3 for Emacs, and those of 2004 for XEmacs).")

Notice the name of this variable, its docstring (which doesn’t describe it) and the peculiar please-ignore-this-line value. Why would you possibly abuse it for what looks like something for a manual?

(condition-case nil
      (require 'easymenu)
       cperl-menu cperl-mode-map "Menu for CPerl mode"
          ["Tips" (describe-variable 'cperl-tips) t]
          ["Problems" (describe-variable 'cperl-problems) t]
          ["Speed" (describe-variable 'cperl-speed) t]
          ["Praise" (describe-variable 'cperl-praise) t]
          ["Faces" (describe-variable 'cperl-tips-faces) t]
          ["CPerl mode" (describe-function 'cperl-mode) t]
          ["CPerl version"
           (message "The version of master-file for this CPerl is %s-Emacs"
                    cperl-version) t]))))
  (error nil))

So, that’s why. Clicking on these menu items gives you a poor substitute for a properly written manual.