{ 
  push @stack,$scalar;
  $scalar=undef;
 
  ... some code...
 
  $scalar=shift @stack;
}

##</code><code>##

package NewStdScalar;
require Tie::Scalar;
 
@ISA = qw(Tie::StdScalar);
 
sub FETCH { return ${+shift}++ }
 
package main;
 
tie our $scalar, 'NewStdScalar';
 
$scalar=0;
 
print $scalar;             # 0
 
{
  local $scalar="---";     # ---
  print $scalar;
}
   
print $scalar;             # 1