sub a { 
  my($var) = @_; 
  if(!$evaled) { 
    eval(makesub("somesub")); 
    $evaled=1; 
  } 
  somesub();  # only place I call it from.
              # only want to eval once per
              # program execution, but have 
              # access to the my variables for
              # each calling of "a"
}