#!/usr/bin/perl

# https://perlmonks.org/?node_id=11101225

use strict;
use warnings;

my $sentence = "this is the text to play with";
my $ngramWindow_MIN = 2;
my $ngramWindow_MAX = 3;

my ($low, $high) = ($ngramWindow_MIN - 1, $ngramWindow_MAX - 1);

$sentence =~ /(?<!\S)\S+(?: \S+){$low,$high}?(?!\S)(?{
  print "START INDEX: @{[$` =~ tr| || ]} : $&\n"
  })(*FAIL)/;