Update: fixed code to work with zby's case and hopefully any other case.
Update: code won't work with duplicates in the second list

Not exactly vastly mystical but this should do the trick (although it hasn't been thoroughly tested) 

use strict;

my @a = qw/ fred bob joe jim mary elaine /;
my @b = qw/ frank joe jim mary bob /;

print "LCS[anjiro] - ", join($", get_lcs(\@a, \@b)), $/;

@a = qw/ a b c /;
@b = qw/ a b x c /;

print "LCS[zby]    - ", join($", get_lcs(\@a, \@b)), $/;

sub get_lcs {
  my @a = @{ +shift };
  my @b = @{ +shift };

  my %map = map { $b[$_] => $_ } 0 .. $#b;

  my(@lcs, @tmp);
  for(0 .. $#a) {
    next unless exists $map{$a[$_]}
                or $a[$_ + 1] eq $b[$map{$a[$_]} + 1];

    push @tmp, $a[$_] if $a[$_] eq $b[$map{$a[$_]}];

    if($a[$_ + 1] ne $b[$map{$a[$_]} + 1]) {
      @lcs = @tmp if @tmp > @lcs;
      @tmp = ();
    }
  }
  @lcs = @tmp if @tmp > @lcs;

  return @lcs;
}

__output__

LCS[anjiro] - joe jim mary
LCS[zby]    - a b

[download]
You might also find some roughly applicable questions under Longest Common Substring.
HTH

_________
broquaint

In reply to Re: Finding largest common subset in lists? by broquaint
in thread Finding largest common subset in lists? by anjiro

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.