I think that's quite inaccurate. Lexical variables are cleared on block exit and re-used unless there are still references to them.
That is an optimization, and the documentation specifically warns against relying on it as your example does.

The "discarded" doesn't mean literally freeing the pad SV. Here: 

$ perl5.10.0 -we'{ my $x; sub foo { eval q!print $x! } foo }'
Use of uninitialized value $x in print at (eval 1) line 1.
$ perl5.10.0 -we'{ my $x; sub foo { eval q!print $x! } } foo'
Variable "$x" is not available at (eval 1) line 2.
Use of uninitialized value $x in print at (eval 1) line 1.

[download]
$x is logically discarded and hence "not available" after the scope is exited, even though the SV may still stay in the pad.

In reply to Re^2: Rules of Lexical Scoping by ysth
in thread Rules of Lexical Scoping by ysth

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.