If I understand correctly, you want the list of elements common to all, right?. There is a fairly simple way to do that.

The list must be a subset of any row, so start with the first and make a hash of it, called %common. Look at the next row, and delete any key in %common which is not there. Lather, rinse repeat. Here's the code:

sub common {
    my $num = @_;
    my (%common, %test);
    $_ = shift;
    @common{@$_} = () x @$_; # second use is scalar context
    while ( $_ = shift) {
        %test = ();
        @test{@$_} = () x @$_;
        delete @common{  grep { ! exists $test{$_} } keys %common};
    }
    [ [keys %common] x $num ];
}

[download]
delete takes a list of arguments, which is provided by the slice over %common. The keys for that slicee are selected by grep as those which are not present in the current array, as represented by keys %test.

This approach discards ordering.

Update: Modified code to return ref to AoA corresponding to $test of the root node. U2 fixed typo in code, parens for curlies in %common init, may save some time.

After Compline,
Zaxo

In reply to Re: Remove unique elements from a list of lists by Zaxo
in thread Remove unique elements from a list of lists by simon.proctor

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.