#!/usr/bin/perl -w
# htmlsub - make substitutions in normal text of HTML files
# from Gisle Aas <gisle@aas.no>

sub usage { die "Usage: $0 <from> <to> <file>...\n" }

my $from = shift or usage;
my $to   = shift or usage;
usage unless @ARGV;

# Build the HTML::Filter subclass to do the substituting.

package MyFilter;
require HTML::Filter;
@ISA=qw(HTML::Filter);
use HTML::Entities qw(decode_entities encode_entities);

sub text
{
   my $self = shift;
   my $text = decode_entities($_[0]);
   $text =~ s/\Q$from/$to/go;       # most important line
   $self->SUPER::text(encode_entities($text));
}

# Now use the class.

package main;
foreach (@ARGV) {
    MyFilter->new->parse_file($_);
}