As far as I can tell, your writeup captures everything about local except the fact that, as an efficiency hack, Perl doesn't use assignment to implement it, but aliasing.

In other words, local $_ is more like: 

  {
    my $saved = \$_;
    my $new;
    *_ = \$new;
    # ...
    *_ = $saved
  }

[download]
Most of the time, this has the same effect as assignment, but is faster. That's why Perl 5 uses it.

Unfortunately, this improvement in Perl 5 actually broke some code that expected localization to be visible via all names of aliased variables (e.g. exported variables). In short, you can't usefully localize an exported variable in Perl 5. This is a Bad Thing, and I hope that Larry fixes it somehow.

On the other hand, I hope that Larry finally fixes the name of the operator by renaming it to ``save''.

    -- Chip Salzenberg, Free-Floating Agent of Chaos

In reply to Re: YAlQ: Yet Another local() Question. by chip
in thread YAlQ: Yet Another local() Question. by BlaisePascal

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.