This seems to work: 
use strict;

my @a = qw( fred bob joe jim mary elaine );
my @b = qw( frank joe jim mary bob );
my @result;

while (@a and @a > @result) {
    my $start = 0;
    while (@b - $start > @result) {
        my $end = 0;
        my @maybe = ();
        $end++ while (exists($a[$end]) and $a[$end] eq $b[$start+$end]
+);
        if (--$end > @result) {
            @result = @a[0..$end];
        }
        $start++;
    }
    shift(@a);
}

print "@result\n";

[download]
Note that I am destroying @a !

Jenda
Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows where you live.
   -- Rick Osborne

Edit by castaway: Closed small tag in signature

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

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