#!/usr/bin/perl/

use warnings;
use strict;

my $phrases = [];  # Array of Hashes containing the different
                   # length phrases...the index of each entry
                   # is the number of words in tne phrases, the
                   # hash contains all of the phrases of that length,
                   # exactly as the OP did in the example

my $maxPhraseLen = 4;  # to match the OPs example.  Can be set to any
                       # value from 1 to the Length of the Abstract

my $abstract  = 'Perl is a high-level, general-purpose, interpreted, ';
   $abstract .= 'dynamic programming language.';
my @words = split(/\s+/, $abstract);

die "Max Phrase Length exceeds number of words in abstract: aborting\n"
  if($maxPhraseLen > (scalar @words));
  
foreach my $numWordsInPhrase (1..$maxPhraseLen){
   foreach my $index (0..($#words-$numWordsInPhrase)) {
      my $phrase = "";  # clear out the phrase accumulator
      for(my $i = 0; $i<$numWordsInPhrase; $i++){
         $phrase .= $words[($index+$i)] . ' ';
      }
      $phrases->[$numWordsInPhrase]->{$phrase} = undef;
   }
   
}

print "\n";
foreach(my $i = 1; $i<(scalar @$phrases); $i++){
   print "PHRASE LENGTH $i:\n";
   foreach my $phrase (keys %{$phrases->[$i]}){
      print "   $phrase\n";
   }
}
      
exit(0);