Dear Monks

I would like to extract from an abstract, all unique phrases of two-, three- and four-words length in seperate groups. Order of the words in the phrase must be preserved but the order of the phrases in the output need not be. Using a hash achieves this in addition to removing duplicates if any. Please see below for my solution that achieves what i want.
However, I would like to know what is a better way as this approach will be cumbersome to scale up for phrases of n-words length as n gets larger.

Thanks in advance.

#!/usr/bin/perl

use strict;
use warnings;

my $abstract = 'Perl is a high-level, general-purpose, interpreted, dy
+namic programming language.';

my (%double_words, %triple_words, %four_words);

my @words = split(/\s+/, $abstract);

foreach(0..$#words){
   $double_words{$words[$_].' '.$words[$_+1]}= undef if($_<$#words);
   $triple_words{$words[$_].' '.$words[$_+1].' '.$words[$_+2]}= undef 
+if($_<$#words-1);
   $four_words{$words[$_].' '.$words[$_+1].' '.$words[$_+2].' '.$words
+[$_+3]}= undef if($_<$#words-2);
}

foreach(keys %four_words){ print $_."\n"; } #sample output

[download]
Sample output of all four-word phrases:

general-purpose, interpreted, dynamic programming
a high-level, general-purpose, interpreted,
Perl is a high-level,
interpreted, dynamic programming language.
is a high-level, general-purpose,
high-level, general-purpose, interpreted, dynamic

In reply to extract phrases of n-words length by arun_kom

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