in reply to Re^4: Word density
in thread Word density

Perhaps this will do what you want? 
push(@words_bi,  $words[$_-1] . $words[$_]  );

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Update: Oops, the words will be stuck together. My bad. 
push(@words_bi,  $words[$_-1] . " " . $words[$_]  );

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"Age is nothing more than an inaccurate number bestowed upon us at birth as just another means for others to judge and classify us"

sulfericacid

In Section Seekers of Perl Wisdom