because the map generates an anon array that is an "extra step" and that array is copied to @a.

No array is created. One million scalars are created, but the question wasn't about that snippet. It was provided as a baseline.

In your later code, you have a map within a map which is similar to a foreach within a foreach. So it is going to run like 1 million times slower.

No, it's not multiplicative like a foreach in a foreach. It's additive like a foreach after a foreach. 

my @array = map A, map B, LIST;

[download]

is functionally similar to 

my @list1;
for (LIST) {
    push @list1, B;
}
my @list2;
for (@list1) {
    push @list2, A;
}
my @array = @list2;

[download]

Snippet three should take about 0.21 + (0.21-0.06) = 0.56, but it's taking 31.48 due to excessive paging. Why is it paging so much?

In reply to Re^2: What could cause excessive page faults? by ikegami
in thread What could cause excessive page faults? by BrowserUk

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.