Emacs: perl-mode vs cperl-mode

In emacs, there are 2 modes for Perl: perl-mode and cperl-mode . Both are included in emacs 23. perl-mode is the simpler of the two. This page is a comparisonn of their syntax coloring features.

By default, perl-mode is loaded when you open a Perl script.

perl-mode is originally written by William F Mann (aka Bill Mann). 1023 lines of code.

is originally written by William F Mann (aka Bill Mann). 1023 lines of code. cperl-mode is primarily written by Ilya Zakharevich. 8987 lines of code.

Syntax Coloring Comparison

In emacs, the global variable “font-lock-maximum-decoration” controlls how much coloring you want. The syntax coloring in the above pages have “font-lock-maximum-decoration” set at 2.

If you find cperl's coloring too wild, you can set the value to 1. (just Alt + x set-variable ) or put this in your emacs init file: (setq font-lock-maximum-decoration 2) .

Alt + x describe-variable to see full doc of this variable. Note: not all modes support font-lock-maximum-decoration . cperl-mode does.

Feature Comparison

cperl-mode offers much more features than perl-mode .

perl-mode Doc String

perl-mode is an interactive compiled Lisp function in `perl-mode.el'. (perl-mode) Major mode for editing Perl code. Expression and list commands understand all Perl brackets. Tab indents for Perl code. Comments are delimited with # ...

. Paragraphs are separated by blank lines only. Delete converts tabs to spaces as it moves back. key binding --- ------- TAB perl-indent-command (that binding is currently shadowed by another mode) ESC Prefix Command : .. ; perl-electric-terminator { perl-electric-terminator } perl-electric-terminator DEL backward-delete-char-untabify C-M-a perl-beginning-of-function C-M-e perl-end-of-function C-M-h perl-mark-function C-M-q perl-indent-exp Variables controlling indentation style: …

cperl-mode Doc String

cperl-mode is an interactive compiled Lisp function in `cperl-mode.el'. It is bound to <menu-bar> <file> <lang-modes> <perl>. (cperl-mode) Major mode for editing Perl code. Expression and list commands understand all C brackets. Tab indents for Perl code. Paragraphs are separated by blank lines only. Delete converts tabs to spaces as it moves back. Various characters in Perl almost always come in pairs: {}, (), [], sometimes <>. When the user types the first, she gets the second as well, with optional special formatting done on {}. (Disabled by default.) You can always quote (with C-q) the left "paren" to avoid the expansion. The processing of < is special, since most the time you mean "less". CPerl mode tries to guess whether you want to type pair <>, and inserts is if it appropriate. You can set `cperl-electric-parens-string' to the string that contains the parenths from the above list you want to be electrical. Electricity of parenths is controlled by `cperl-electric-parens'. You may also set `cperl-electric-parens-mark' to have electric parens look for active mark and "embrace" a region if possible.' CPerl mode provides expansion of the Perl control constructs: if, else, elsif, unless, while, until, continue, do, for, foreach, formy and foreachmy. and POD directives (Disabled by default, see `cperl-electric-keywords'.) The user types the keyword immediately followed by a space, which causes the construct to be expanded, and the point is positioned where she is most likely to want to be. eg. when the user types a space following "if" the following appears in the buffer: if () { or if () } { } and the cursor is between the parentheses. The user can then type some boolean expression within the parens. Having done that, typing C-c C-j places you - appropriately indented - on a new line between the braces (if you typed C-c C-j in a POD directive line, then appropriate number of new lines is inserted). If CPerl decides that you want to insert "English" style construct like bite if angry; it will not do any expansion. See also help on variable `cperl-extra-newline-before-brace'. (Note that one can switch the help message on expansion by setting `cperl-message-electric-keyword' to nil.) C-c C-j is a convenience replacement for typing carriage return. It places you in the next line with proper indentation, or if you type it inside the inline block of control construct, like foreach (@lines) {print; print} and you are on a boundary of a statement inside braces, it will transform the construct into a multiline and will place you into an appropriately indented blank line. If you need a usual `newline-and-indent' behavior, it is on C-j, see documentation on `cperl-electric-linefeed'. Use C-c C-t to change a construction of the form if (A) { B } into B if A; key binding --- ------- C-c Prefix Command TAB cperl-indent-command (that binding is currently shadowed by another mode) C-j newline-and-indent ESC Prefix Command ( cperl-electric-paren ) cperl-electric-rparen : cperl-electric-terminator ; cperl-electric-semi < cperl-electric-paren [ cperl-electric-paren ] cperl-electric-rparen { cperl-electric-lbrace } cperl-electric-brace DEL cperl-electric-backspace C-M-q cperl-indent-exp C-M-\ cperl-indent-region C-M-| cperl-lineup C-c C-a cperl-toggle-auto-newline C-c C-b cperl-find-bad-style C-c C-d cperl-here-doc-spell C-c C-e cperl-toggle-electric C-c C-f auto-fill-mode C-c C-h Prefix Command C-c C-j cperl-linefeed C-c C-k cperl-toggle-abbrev C-c C-n cperl-narrow-to-here-doc C-c C-p cperl-pod-spell C-c C-t cperl-invert-if-unless C-c C-v cperl-next-interpolated-REx C-c C-w cperl-toggle-construct-fix C-c C-x cperl-next-interpolated-REx-0 C-c C-y cperl-next-interpolated-REx-1 C-c C-h F cperl-info-on-command C-c C-h P cperl-perldoc-at-point C-c C-h a cperl-toggle-autohelp C-c C-h f cperl-info-on-current-command C-c C-h p cperl-perldoc C-c C-h v cperl-get-help Setting the variable `cperl-font-lock' to t switches on font-lock-mode (even with older Emacsen), `cperl-electric-lbrace-space' to t switches on electric space between $ and {, `cperl-electric-parens-string' is the string that contains parentheses that should be electric in CPerl (see also `cperl-electric-parens-mark' and `cperl-electric-parens'), setting `cperl-electric-keywords' enables electric expansion of control structures in CPerl. `cperl-electric-linefeed' governs which one of two linefeed behavior is preferable. You can enable all these options simultaneously (recommended mode of use) by setting `cperl-hairy' to t. In this case you can switch separate options off by setting them to `null'. Note that one may undo the extra whitespace inserted by semis and braces in `auto-newline'-mode by consequent DEL. If your site has perl5 documentation in info format, you can use commands C-c C-h f and C-c C-h F to access it. These keys run commands `cperl-info-on-current-command' and `cperl-info-on-command', which one is which is controlled by variable `cperl-info-on-command-no-prompt' and `cperl-clobber-lisp-bindings' (in turn affected by `cperl-hairy'). Even if you have no info-format documentation, short one-liner-style help is available on C-c C-h v, and one can run perldoc or man via menu. It is possible to show this help automatically after some idle time. This is regulated by variable `cperl-lazy-help-time'. Default with `cperl-hairy' (if the value of `cperl-lazy-help-time' is nil) is 5 secs idle time . It is also possible to switch this on/off from the menu, or via C-c C-h a. Requires `run-with-idle-timer'. Use C-M-| to vertically lineup some construction - put the beginning of the region at the start of construction, and make region span the needed amount of lines. Variables `cperl-pod-here-scan', `cperl-pod-here-fontify', `cperl-pod-face', `cperl-pod-head-face' control processing of POD and here-docs sections. With capable Emaxen results of scan are used for indentation too, otherwise they are used for highlighting only. Variables controlling indentation style: … DO NOT FORGET to read micro-docs (available from `Perl' menu) or as help on variables `cperl-tips', `cperl-problems', `cperl-praise', `cperl-speed'.

Setting-up cperl-mode as Default

If you always want cperl-mode to be loaded, put: (defalias 'perl-mode 'cperl-mode) in your emacs init file. This way, when you Alt + x perl-mode , it'll be Alt + x cperl-mode .

Alternatively, you can put the following:

( setq auto-mode-alist ( rassq-delete-all 'perl-mode auto-mode-alist )) ( add-to-list ' auto-mode-alist '( "\\.\\(p\\([lm]\\)\\)\\'" . cperl-mode)) ( setq interpreter-mode-alist ( rassq-delete-all 'perl-mode interpreter-mode-alist )) ( add-to-list ' interpreter-mode-alist '( "perl" . cperl-mode)) ( add-to-list ' interpreter-mode-alist '( "perl5" . cperl-mode)) ( add-to-list ' interpreter-mode-alist '( "miniperl" . cperl-mode))

This way, you can still call perl-mode if you do need it, or want to experiment with the two modes.

[see Learn Perl in 1 Hour]