Between 5.10.0 and 5.12.0 the way $#array is handled in rvalue context changed. In lvalue context, that expression returns a magic value which, when assigned to, updates the array's length. In 5.10.0, a similar magical value was also returned in rvalue context, which delayed evaluation of the array's length until the second (left-most) split was being done. In 5.12.0 onwards, the rvalue $#array expression is evaluated immediately.

This appears to be intentional: 

commit 02d85cc37a4acecafdc2f0b45640b03cd1f4ac71
Author:     Eric Brine <ikegami@adaelis.com>
AuthorDate: Fri Oct 23 19:05:40 2009 -0400

    Avoid adding magic with rvalue $#a

[download]

Dave.

In reply to Re: Odd splice behavior between perl/OS versions by dave_the_m
in thread Odd splice behavior between perl/OS versions by SimonSaysCake

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.