#!/usr/bin/perl -l

use strict;
use warnings;

# build word list in %words
my %words;
open my $dict, "/usr/dict/words";
chomp, $words{lc $_} = 1 while <$dict>;  # UPDATE:  added 'lc'
close $dict;

my $str = "perfumesmellslikecheese";

$str =~ m{
  ^                          # anchor to beginning of string
  (?{ [ ] })                 # start $^R as an empty array ref
  (?:                        # match this block <<
    (\w{2,})                   # capture 2 or more letters to $1
    (?(?{ $words{lc $1} })     # if lowercase '$1' is in %words...
      (?{ [ @{$^R}, $1 ] })      # add this word to the current list
      |                        # otherwise...
      (?!)                       # fail (force \w{2,} to backtrack)
    )
  )+                         # >> one or more times
  $                          # anchor to end of string
  (?{ print "@{$^R}" })      # print the words (with spaces)
  (?!)                       # fail (cause everything to backtrack)
}x;