package MyUserAgent;

use base 'WWW::Mechanize';
use URI;

sub file_root {
  my $self = shift;
  if (@_) {
    $self->{_file_root} = shift;
  }
  $self->{_file_root};
}

sub send_request {
  my $self = shift;
  my $request = shift;

  my $old_uri = $request->uri;
  if ($old_uri->scheme eq 'bar') {
    if ($old_uri->path =~ m{\A/..(/|\z)}) {
      return LWP::UserAgent::_new_response($request, 404,
               "File not found - URL begins with /..");
    }
    my $new_uri = URI->new("file:".$self->file_root."/".$old_uri->path);
    $request->uri($new_uri);
  }
  my $ret = $self->SUPER::send_request($request, @_);
  $request->uri($old_uri);
  $ret;
}