let is like temp but it's only useful inside of rules. If the rule succeeds, then the variable keeps the hypothesized value. If the rule fails, then the variable loses its hypothesized value and thus reverts back to whatever value it had before (if any).
I've quickly searched around and indeed it seems to be so. That is, let is to be used in closures embedded in rules.

Due to the deep analogy between rules and subs I wonder wether the same mechanism could be made to work also for the latter ones (using the return value for success): I do not see any immediate use, but I bet someone could find one.

Well, however this is probably not best discussed here...

In reply to Re^4: perl5 vs perl6 by blazar
in thread perl5 vs perl6 by jbrugger

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.