sub x{ 
    my( @a, @b ) = @_; 
    print "a:[@a]\nb:[@b]"; 
};

@x = 1..10; 
@y = 'a'..'f';;
print "x:[@x]\ny:[@y]";;
x:[1 2 3 4 5 6 7 8 9 10]
y:[a b c d e f]

x( @x, @y );;
a:[1 2 3 4 5 6 7 8 9 10 a b c d e f]
b:[]

##</code><code>##

sub MI {
    my( $string_es, $string_en, $hash_es, $hash_en ) = @_;

    my $prob_es = ( keys %$hash_es ) / 6939873;
    my $prob_en = ( keys %$hash_en ) / 6939873;

    my $common = 0;
    exists $hash_en->{ $_ } and ++$common for keys %$hash_es;
    
    my $prob_es_en= ( $common ) / 6939873;
    $prob_es_en = ( $prob_es_en + ( $prob_es * $prob_en * 0.1) ) / 1.1;
    
    my $mi = $prob_es_en * log( $prob_es_en / ( $prob_es * $prob_en ) );
    return $mi;
}

##</code><code>##

#create hash files from ngram statistics
my %hash_en;
to_hash( \%hash_en, $file_in_en );
my %hash_es;
to_hash( \%hash_es, $file_in_es );

...

sub to_hash {
    my( $href, $file ) = @_;

    open(FILE, "<$file");
    foreach my $l (<FILE>) {
        my( $ngram, $line ) = split /\t/, $l;
        push @{ $href->{ $ngram } }, $line;
    }
    close FILE;
}