The following may get you headed in a useful direction:

use strict;
use warnings;
use List::Compare;

my @words = qw(dictate world mamal);
my %dict;

# Build a lookup for the dictionary words
while (defined (my $word = <DATA>)) {
    chomp $word;
    next unless length $word;
    my @bigrams = grep length == 2, map {substr $word, $_, 2} 0 .. len
+gth ($word) - 1;
    
    next unless @bigrams;
    $dict{$word} = \@bigrams;
}

# Process the given words
for my $word (@words) {
    my @bigrams = grep length == 2, map {substr $word, $_, 2} 0 .. len
+gth ($word) - 1;

    next unless @bigrams;

    for my $dictWord (keys %dict) {
        my $lc = List::Compare->new($dict{$dictWord}, \@bigrams);
        my @common = $lc->get_intersection ();
        my $diceCoef = 2 * @common / (@bigrams + @{$dict{$dictWord}});
        
        next unless $diceCoef;
        print "Dice coefficient for '$word' and '$dictWord' is $diceCo
+ef\n";
    }
}


__DATA__
a
small
dictionary
of
words
[download]

Prints:

Dice coefficient for 'dictate' and 'dictionary' is 0.4
Dice coefficient for 'world' and 'words' is 0.5
Dice coefficient for 'mamal' and 'small' is 0.5
[download]