#!perl -wl

my @L1 = qw/A b c de fgh ijk lmno pqrst uvwxyz/;
my @L2 = qw/a b c de fgh ijk lmnO pqrsT uvwxyZ/;
my @MATCHES = ();
my $LMATCH = 0;

for $I1 (sort{length($b)<=>length($a)}@L1){
        last if length($I1) < $LMATCH;
        for $I2 (grep{$_ eq $I1}sort{length($b)<=>length($a)}@L2){
                $LMATCH = length($I2);
                push @MATCHES, $I1;
        }
}

print "LIST1: " . scalar @L1 . " items
LIST2: " . scalar @L2 . " items
MATCHES: @MATCHES";