This is what I ended up with and am using (incorporating fizbin's points).

I've changed the definition of a word.

• Hyphenated words are now separated and treated separately
• Accented words are now ascii-ised

The other difference is that HTML entities are decoded while extracting text from the HTML.
All the text (apart from curly punctuation) is Latin 1.

#!/usr/bin/perl

use strict;
use warnings;
use locale;

my $config = {
  stop => 'data/stop.txt',
  minw => 3,
  maxw => 20,
};

my $words = q(
  and cat's O'Rielly counter-productive crèche 
  2000 1980s 777777 x0000
  repeat repeat repeat
);

my %keywords = get_word(lc $words);

for (keys %keywords){
  print "$_\n";
}

sub get_word{
  
  my ($text) = @_;
  
  my ($min, $max) = ($config->{minw}, $config->{maxw});
  my %stop = get_stop($config->{stop});
  my %acc  = get_accent();
  my %pat  = get_patterns();
  my %keywords;
  for ($text){
    s/$pat{rsqu}/'/g;
    s/$pat{hyph}/ /g;
    s/(.)/$acc{$1}?$acc{$1}:$1/eg;
  }
  my @words = ($text =~ /$pat{word}/g);
  my %seen;  
  for (@words){
    s/$pat{posv}//;
    s/$pat{apos}//g;
    next if length() < $min or length() > $max;
    next if /$pat{numb}/ and not /$pat{date}/;
    s/$pat{tail}// if /$pat{numb}/;
    next if exists $stop{$_};

    unless ($seen{$_}){
      $seen{$_}++;
      $keywords{$_} = undef;
    }
  }
  return %keywords;
}    

sub get_patterns{
  my %pat = (
    posv => q/'s$/,            # possessive s
    apos => qr/'/,             # apostrophe
    hyph => qr/-/,             # hyphen
    numb => qr/\d/,            # number
    date => qr/^[12]\d{3}s?$/, # date like 1960, 1990s
    rsqu => qr/\x{2019}/,      # right single quote
    tail => qr/s$/,            # trailing s for stripping off numbers
    word => qr/([\w']+)/,      # word that may contain apostrophe
  );
  return %pat;
}

sub get_accent{
  return qw(
    À A Á A Â A Ã A Ä A Å A Æ AE 
    Ç C 
    È E É E Ê E Ë E 
    Ì I Í I Î I Ï I 
    Ð TH Ñ N 
    Ò O Ó O Ô O Õ O Ö O Ø O 
    Ù U Ú U Û U Ü U 
    Ý U Þ TH ß ss 
    à a á a â a ã a ä a å a æ ae 
    ç c 
    è e é e ê e ë e 
    ì i í i î i ï i 
    ð th ñ n 
    ò o ó o ô o õ o ö o ø o 
    ù u ú u û u ü u 
    ý y þ th ÿ y
  );
}

sub get_stop {
  # load stop word file
  # sample
  my %stop = (
    and => undef,
    the => undef,
    any => undef,
  );
  return %stop;
}
[download]

output:

---------- Capture Output ----------
> "C:\Perl\bin\perl.exe" clean_words.pl
1980
orielly
productive
creche
cat
counter
2000
repeat

> Terminated with exit code 0.
[download]