Due to carelessness on my part I had a shed load of html containing suspect characters. The difficulty was having a possible combination of x80-x9F (frowned on by w3c), unicode and html entities (including numeric entities).
The strategy I arrived at was to:
  1. decode any entities present
  2. convert x80-x9F to unicode equivalents
  3. encode 'unsafe' characters

This will ensure, hopefully, consistant html and prevent problems during any future processing.

What do you reckon? 

#!/usr/bin/perl

use strict;
use warnings;
use HTML::Entities;

my $lookup = get_cp1252_lookup();

my $str = join('',
  chr(0x93), 'double', chr(0x94),
  chr(0x201C), 'double', chr(0x201D),
  '‘single’'
);

# "replaces HTML entities...
#  with the corresponding Unicode character"
decode_entities($str); 

# replaces x80-x9f with unicode equivalant
$str =~ s/([\x80-\x9f])/$lookup->{sprintf("%x", ord($1))}/eg;

# "replaces unsafe characters...
#  with their entity representation"
encode_entities($str);

print "$str\n";

sub get_cp1252_lookup{
  
  open my $fh, '<', 'cp1252_to_unicode.txt'
    or die "can't open input: $!";
  
  my $lookup;
  
  while (<$fh>){
    my ($cp1252, $utf8_str, $name) = split /\t/;
    $cp1252 =~ s/0x//;
    my $utf8 = $utf8_str =~ / /? '':chr(oct($utf8_str));
    $lookup->{$cp1252} = $utf8;
  }
  return $lookup;
}

__END__
output:

&ldquo;double&rdquo;&ldquo;double&rdquo;&lsquo;single&rsquo;

extract from cp1252_to_unicode.txt:

0x91    0x2018    #LEFT SINGLE QUOTATION MARK
0x92    0x2019    #RIGHT SINGLE QUOTATION MARK
0x93    0x201C    #LEFT DOUBLE QUOTATION MARK
0x94    0x201D    #RIGHT DOUBLE QUOTATION MARK

[download]
Many thanks to all the monks who have helped.
John

In reply to Fixing suspect characters in HTML by wfsp

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