my %pairs;
local $/;

my $data = <DATA>;
my @words = split /\W+/, lc($data_;

$pairs{ $words[$_].' '.$words[$_+1] }++ for 0..$#words-1;

print "$pairs{$_}\t$_\n" 
    for sort { $pairs{$b}<=>$pairs{$a} } keys %pairs;

__DATA__
To be or not to be, that is the question
Ask not what your country can do for you but what you can do for your 
+country
I think therefore I am
I drink therefore I am I'm drunk therfore I was
Alas twas not to be
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