package WordCount;
use strict;
use warnings;
use Exporter qw<import>;
our @EXPORT_OK = qw<count_words>;

sub count_words {
  my ($sentence) = @_;
  my %word_count;
  $sentence =~ s/(.)/\L$1/gi; # force everything to lower case
# [\w\d]+ matches 1 or more "word" or decimal characters
# (?:'t)? matches optional apostrophe t
# the `?:` means a non capturing set of parentheses
# the `gi` at the end means global search and case insensitive
  $word_count{$_}++ foreach ($sentence =~ m/([\w\d]+(?:'t)?)/gi);
  return \%word_count;
}

1;