[Templates] assigning to scalar passed as scalar reference

[Lee.M]

Hello TT friends,

I want to do this:

  my $var = '';

   $tt->process($tmplt, { var => \$var}, $out);

   print "var is now $var\n"; # var is now new value

and allow the template to set its value

[% var = 'new value' %] just changes it from a scalar reference to a  
string

is there anyway to accomplish this pseudo code:

[% ${var} ='new value' %]


TIA!