In each case I use (1..2). Is it a different list each time?

What I called caching is actually constant flattening. That means each op instance is independent.

You only visit each element of each flattened list once. So if you had changed it, you would never know.

The bug is that the "constants" of the list into which 1..2 is flattened aren't marked as read-only.

Except "for constant .. constant" is optimised to not flatten the list. And with this, my question is answerd. 

>perl -le"for (1..2) { print $_++ for 1..2 }"
1
2
1
2

# Disables the "for constant .. constant" optimisation
>perl -le"for (1..2) { print $_++ for (),1..2 }"
1
2
2
3

>perl -le"for (1..2) { map print($_++), 1..2 }"
1
2
2
3

[download]

In reply to Re^6: list assignment and undef by ikegami
in thread list assignment and undef by ig

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.