use Math::Combinatorics qw( combine);
my @collection; # list of strings
my @tuples = combine( 2, @collection);
my @similarity = sort { similarity($a) <=> similarity($b) } @tuples;

sub similarity {
    my $tupel = shift;
    my $value;
    ...
    # determine similarity
    # between $tupel->[0] and $tupel->[1]
    # and store into $value
    ...
    return $value;
}

##</code><code>##

my @similarity = map { $_->[0] }
                 sort { $a->[1] <=> $b->[1] }
                 map { [ $_, similarity($_) ] } @tuples;