code: public void registerSpecialVariableProcessor(@Nonnull final SpecialVariableProcessor processor) {
      assertNotNull("Processor is null", processor);
  
      for (final String varName : processor.getVariableNames()) {
        assertNotNull("A Special Var name is null", varName);
        if (mapVariableNameToSpecialVarProcessor.containsKey(varName)) {
          throw new IllegalStateException("There is already defined processor for " + varName);
        }
        mapVariableNameToSpecialVarProcessor.put(varName, processor);
      }
    }
docs: It allows to register a special variable processor which can process some special global variables
  
  @param processor a variable processor to be registered, it must not be null
  @see SpecialVariableProcessor