You can also complicate it to avoid the loop (in fact, disguise it as a repetition) and the // operator: 
push @{ $h{$_} }, shift @B for (@A, reverse @A) x (@B / @A / 2),
                               (@A, reverse @A)[ 0 .. @B % (2 * @A) - 
+1 ];

[download]

Update: Another idea: 

for my $i (0 .. $#A) {
    $h{ $A[$i] } = [ @B[ grep { my $m = $_ % (2 * @A);
                                grep $_ == $m, $i, 2 * @A - $i - 1
                              } 0 .. $#B ] ];
}

[download]

TIMTOWTDI, an iterator: 

my $iter = do {
    my ($pos, $step) = ('0E0', 1);
    sub {
        my $r = $H{ $A[$pos] } ||= [];
        if ($pos % $#A || $pos =~ /E/) {
            $pos += $step;
        } else {
            $pos .= 'E0';
            $step *= -1;
        }
        return $r
    }
};
push @{ $iter->() }, $_ for @B;

[download]
لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

In reply to Re^3: How to get this not the usual round robin looping [updated] by choroba
in thread How to get this not the usual round robin looping by fidda

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.