HTML::Template

Is there anyway that I can get HTML::Template to evaluate recursively without iteratively recusting templates myself. This is what I'd like be able to do:
#!/usr/bin/perl -w
use strict;
use HTML::Template;
my $s= '<tmpl_var name="foo">';
my $h=HTML::Template->new(scalarref => \$s);
$h->param( foo => '<tmpl_var name="bar">');
$h->param( bar => 'baz');
print $h->output();
but this is the only way I can get it to work:
#!/usr/bin/perl -w
use strict;
use HTML::Template;
my $s= '<tmpl_var name="foo">';
my $h=HTML::Template->new(scalarref => \$s);
$h->param( foo => '<tmpl_var name="bar">');
$s=$h->output();
$h=HTML::Template->new(scalarref => \$s);
$h->param( bar => 'baz');
print $h->output();