# somewhere in a Renderer subclass...
sub POST {
  my $self = shift;
  my $filename = $self->cgi->param('file');
  my $type = $self->cgi->uploadInfo($filename)->{'Content-Type'};
  if ( $type eq 'text/html' ) {
    # do something with the HTML
  }
  elsif ( $type eq 'image/gif' ) {
    # do something with the GIF
  }
  # ...
}