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RFC 347 (v2) Remove long-deprecated $* (aka $MULTILINE_MATCHING)

From:
Perl6 RFC Librarian
Date:
September 30, 2000 23:32
Subject:
RFC 347 (v2) Remove long-deprecated $* (aka $MULTILINE_MATCHING)
Message ID:
20001001063007.2302.qmail@tmtowtdi.perl.org
This and other RFCs are available on the web at
  http://dev.perl.org/rfc/

=head1 TITLE

Remove long-deprecated $* (aka $MULTILINE_MATCHING)

=head1 VERSION

  Maintainer: Hugo van der Sanden <hv@crypt0.demon.co.uk>
  Date: 29 Sep 2000
  Last Modified: 30 Sep 2000
  Mailing List: perl6-language-regex@perl.org
  Number: 347
  Version: 2
  Status: Frozen

=head1 ABSTRACT

The magic $* variable (known in English as $MULTILINE_MATCHING)
has been deprecated for years. It is time to kill it.

=head1 DESCRIPTION

In days of yore, you would set $* to 1 to achieve in all regexps
the same as you can now achieve on a per-regexp basis with the
/m flag. Nowadays, when most perl programmers have never heard
of it, it is an accident waiting to happen and requires ugly
additional cruft for the defensive programmer to avoid.

The particular danger of $* is its 'action at a distance' effect:
as a global variable, its effect reaches into and out of scopes
that we normally expect to protect us.

=head1 MIGRATION

The long deprecation cycle helps here. p52p6 should complain and
die if it sees any attempt to set $* or $MULTILINE_MATCHING to a
non-zero value, or any attempt to alias it other than in English.
It should silently (or maybe with a warning) ignore any attempt to
set it to a zero value, and silently (or maybe with a warning)
replace any attempt to read it with a constant undef.

=head1 IMPLEMENTATION

This only simplifies the regexp engine, and should help fix some
longstanding bugs in the scope of /m. There is a bit of work to
do to extricate it, but nothing seriously difficult.

=head1 REFERENCES

perlvar manpage for discussion of $*




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