[% setvar title Proposal to utilize C<*> as the prefix to magic subroutines %]

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TITLE

Proposal to utilize * as the prefix to magic subroutines

VERSION

  Maintainer: Jonathan Scott Duff <duff@pobox.com>
  Date: 7 Aug 2000
  Last Modified: 1 Sep 2000
  Mailing List: perl6-language@perl.org
  Number: 59
  Version: 2
  Status: Developing

ABSTRACT

Perl has always claimed the ALL-CAPS names for itself, I propose we give them back to the programmer.

DESCRIPTION

Perl steals subroutine names from the programmer. By prefixing the Perl-special subroutines with a character that is not a valid prefix for Perl programmers, we separate what belongs to Perl and what belongs to the user.

With the proliferation of special subroutine names (BEGIN, END, INIT, CHECK, etc.) the all capital subroutine names available to the programmer has steadily shrunk. Rather than stealing subroutines from the programmer, we should create a space just for Perl.

	sub *BEGIN {
	    # do compile-time stuff
	    # Perl-special 
	}

	sub BEGIN {
	    # No relation to the former. Purely user space.
	    # The user may have his/her own reasons for naming his
	    # subroutines this way.  (e.g., it fits the conception model
	    # that the software is build upon/around/through)
	}

The visual distinction lets the programmer know that something special is happening here and that this is not your average run-of-the-mill subroutine. The added * prefix also serves as a guide to the perl compiler that these subroutines may be treated specially.

Another area where could be useful is in conjunction with Damian Conway's want() proposal. As his proposal currently stands, the programmer can not name a package LIST or SCALAR and use it with the proposed want(). Perl has always claimed all lowercase package names for itself, but never ALLCAPS package names.

Examples

	switch ([want]) {
	    case '*LIST'	{ return @array; }
	    case '*SCALAR'	{ return $foo; }
	    case 'LIST'		{ return $MyListObj; }
	}

	sub *BEGIN	{ ... }
	sub *END	{ ... }
	sub *INIT	{ ... }
	sub *AUTOLOAD	{ ... }
	sub *TIESCALAR	{ ... }
	sub *FETCH	{ ... }  

Potential problems

Makes Perl-special subroutines different from user subroutines. This implies yet another special case.

IMPLEMENTATION

Um ... that's up to the internals people.

REFERENCES

Perl 5.6.0 documentation

RFC 21 (v1): Replace wantarray with a generic want function