code: void insertFunctionsAndVariables(TokenList tokens ) {
          TokenList.Token t = tokens.getFirst();
          while( t != null ) {
              if( t.getType() == Type.WORD ) {
                  Variable v = lookupVariable(t.word);
                  if (v != null) {
                      t.variable = v;
                      t.word = null;
                  } else if (functions.isFunctionName(t.word)) {
                      t.function = (new Function(t.word));
                      t.word = null;
                  }
              }
              t = t.next;
          }
      }
docs: Search for WORDS in the token list.  Then see if the WORD is a function or a variable.  If so replace
  the work with the function/variable