anadem,
Perl6 is going to make this a lot easier :-)
I have been fascinated with iterators lately, so this mildly tested code can easily be changed to iterate by any quantity specified. 
#!/usr/bin/perl
use strict;
use warnings;

my @array = 0 .. 30;
my $next = by_groups_of( 3, @array );

while ( my @group = $next->() ) {
    print "@group\n";
}

sub by_groups_of {
    my $by = shift;
    return sub { () } if ! $by || $by =~ /\D/ || ! @_;
    my @list = @_;  # Make a copy in case it changes

    my $end = $#list;
    my $pos = 0;
    my $done;

    return sub {
        return () if $done;
        my $stop = $pos + $by - 1 > $end ? $end : $pos + $by - 1;
        my @sub = @list[ $pos .. $stop ];
        $pos += $by - 1;
        $done = 1 if $stop == $end;
        return @sub;
    }
}

[download]

Cheers - L~R

Update: Also see this node if you need to have modifications to the looping variables modify the array as well

In reply to Re: loop thru 3-element array? by Limbic~Region
in thread loop thru 3-element array? by anadem

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.