[% setvar title Global dynamic variables should remain the default %]

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TITLE

Global dynamic variables should remain the default

VERSION

  Maintainer: Nathan Wiger <nate@wiger.org>
  Date: 28 Sep 2000
  Last Modified: 30 Sep 2000
  Mailing List: perl6-language-strict@perl.org
  Number: 330
  Version: 2
  Status: Frozen

ABSTRACT

Several proposals try to automatically lexicalize variables by default. While this is a nice idea, it defeats the primary purpose of lexical variables: forced declaration and explicit scoping.

Another proposal suggests that users should be forced to declare all variables with my explicitly. Blech. That doesn't make anything easy. Perl is not a B&D language (by default, at least :).

This proposal simply says that variable scoping rules should be the same in Perl 6 as they are currently.

DESCRIPTION

Dynamics are bad in many circumstances. However, standardizing on anything else defeats one of the key purposes of Perl: quick and easy scripting. For fast scripts, lexical variables are a big burden.

RFC 106 makes a good attempt at trying to make lexical variables the default, but unfortunately the only way to get them to work as flexibly as dynamics is to essentially make them into dynamics, as the "liberal approach" to scoping shows. For this reason, dynamics should remain the default and users can explicitly declare lexicals if they so desire. They could also use a pragma, such as use scope (RFC 64), to change the default scoping rules.

One possibility that the author is willing to entertain is making variables dynamic, yet only accessible within a given package. However, Python, PHP, Tcl, and other languages have terrible, terrible problems with stuff like this, so it would have to be implemented extremely carefully. The fact that other languages are broken does not necessarily mean that Perl's implementation would have to be, however.

IMPLEMENTATION

None. Things should stay the same.

MIGRATION

See above.

REFERENCES

RFC 106: Yet another lexical variable proposal: lexical variables made default without requiring strict 'vars'

RFC 16: Keep default Perl free of constraints such as warnings and strict.

RFC 28: Perl should stay Perl.

RFC 64: New pragma 'scope' to change Perl's default scoping

RFC 6: Lexical variables made default