Overall right. Just nitpicking two details.

First, optimization is not a factor. It's simply whether the my gets executed or not.

Second, you're also off on the timing. Clearing occurs at end of scope. It's triggered by the my, but it doesn't occurs when the my is encountered. (By the way, that's also when a new my variable is created if the refcount is greater than 1.)

Both points can be observed in 

sub foo {
   my ($reset) = @_;
   my $x if $reset;   # Will reset at end of scope if $reset is true.
   return ++$x;
}

print foo(0), "\n";  # 1
print foo(0), "\n";  # 2
print foo(1), "\n";  # 3
print foo(0), "\n";  # 1
print foo(0), "\n";  # 2

[download]

In reply to Re^2: static variable hack by ikegami
in thread static variable hack by InfiniteLoop

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.