Thanks to inspiration from BrowserUK and wind (though I still have a ways to go before I grok their replies) I think I have something to share if only for terseness.

#!/usr/bin/env perl

use strict;
use warnings;
use List::Util(qw(min));
use List::MoreUtils(qw(uniq));

my @array = map {[split]} ("11 12", "11 13", "9 8 7", "3 4", "11 4");

my %v2g = ();
my %g2v = ();

for my $i (@array) {
    my @sg = sort {$a<=>$b} uniq grep {defined} (@v2g{@$i}, min @$i);
    my $sg = shift @sg;
    $g2v{$v2g{$_} ||= $sg}->{$_}++ for @$i;
    for my $j (@sg) {
        @v2g{keys %{$g2v{$j}}} = ($sg) x keys %{$g2v{$j}};
        @{$g2v{$sg}}{keys %{$g2v{$j}}} = values %{$g2v{$j}};
        delete $g2v{$j};
    }
}

print join ("\n", map {join " ", sort {$a<=>$b} keys %$_} values %g2v)
+, "\n";

[download]

Output

3 4 11 12 13
7 8 9

About the only thing really new to add to the discussion is that this problem seems to be equivalent to finding the disjoint subgraphs of a vertex adjacency matrix of a non-directed graph. So there's probably an algorithm out there that puts this code's efficiency to shame.

In reply to Re: how to find combine common elements of an array? by jaredor
in thread how to find combine common elements of an array? by ihperlbeg

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.