use strict;
use warnings;
use Smart::Comments '###';

my $abstract    = 'Perl is a high-level, general-purpose, interpreted, dynamic programming language.';
my $MinLength   = 2;#Must be at least 1;
my $MaxLength   = 4;#Must be >= $MinLength

my $MinPosition = $MinLength - 1;#Counting from 0

my (    $ArrayRef,
        $AnswerRef  )   = ();

@$ArrayRef = split(/\s+/, $abstract);
#Iterate through @$ArrayRef
for my $position  (0..($#$ArrayRef-$MinPosition)) {
    #handle the first word with no space
    my $phrase = $ArrayRef->[$position];
    for my $x (1..$MaxLength) {#Build the phrase
        #For all but the first time
        $phrase .= ' ' . $ArrayRef->[$position] if  $x != 1;
        #Load the output
        $AnswerRef->[$x]->{$phrase} = 1 if $x >= $MinLength;
        $position++;
        #Bump up against the end
        last if $position > $#$ArrayRef;
    }
}

#use Smart::Comment.pm
### The unique 3 word phrases are: $AnswerRef->[3]