I wrote about the C-style for() in Re: Re: Believably slow... It is slower than the foreach() style for. Not significantly but slightly. I could only remove a few operations from your code, I noted each spot with an ALTER comment. I think your time is consumed by those print() statement - IO is always expensive.

## Print the given template sections to the supplied filehandle
sub printto
{
  my $self = shift;
  my $fh = shift;
  my $ret = 0;
  my($val,$sec,$v);

  # ALTER - foreach over C-style for
  foreach my $sec_k (@_)
  {
    $sec = $self->[_sec]{$sec_k};
    # ALTER - drop unnecessary defined()
    unless ( $sec )
    {
      # ALTER - remove indirect object syntax
      $fh->print( $self->_nosuchsec($sec_k) );
      next;
    }
    $ret++;
    foreach $v (@$sec)
    {
      if ($v->[_type] == type_text)
      {
        # ALTER - remove indirect object syntax
        $fh->print( $v->[_contents] );
      }
      else
      {
        $val = $self->[_assign]{$v->[_contents]};
        $fh->print(
          defined $val
            ? $val
            : $self->_nosuchvar($val,"\$".$val) );
      }
    }
  }
  return $ret;
}
[download]