Your efficiency note is only true until Perl 5.6.1.

The problem is that Perl builds the return list in place. In old versions it would only allocate the minimum necessary space, moving data every time. The moving of data was a O(n2) bottleneck. Starting in 5.6.1 it will allocate the minimum of the minimum necessary, and the length of the data stack. This results in a power of 2 reallocation strategy that winds up being O(n) in terms of moving data.

To experience the difference that this makes, try running this statement in both a new and old version of Perl: 

my @big_list = map {($_, $_)} 1..50_000;

[download]
If it takes a while, you aren't on 5.6.1 yet. :-)

In reply to Re (tilly) 2: Miniature golf question by tilly
in thread Miniature golf question by nysus

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.