anchor.diff:  
   maybe_cmd options{ backtrack=true; } :
        expr (t_FILLER? t_ASSIGN t_FILLER? expr)? t_FILLER?
  -  //|  t_IDENTIFIER cmd_args //TODO-AC: re-enable once I figure out side-effects/backtracking
  +  |  t_IDENTIFIER cmd_args //TODO-AC: re-enable once I figure out side-effects/backtracking
     ;
   
   cmd_args :
  
positive.code: 
  t_ASSIGN : ASSIGN { offsetTracker.advanceInLine(1); };
  
  t_LPAREN : LPAREN { offsetTracker.advanceInLine(1); bracketStack.push(LPAREN); };
  t_RPAREN : RPAREN { offsetTracker.advanceInLine(1); bracketStack.pop(); };
  t_LCURLY : LCURLY { offsetTracker.advanceInLine(1); bracketStack.push(LCURLY); };
  t_RCURLY : RCURLY { offsetTracker.advanceInLine(1); bracketStack.pop(); };
  t_LSQUARE : LSQUARE { offsetTracker.advanceInLine(1); bracketStack.push(LSQUARE); };
  t_RSQUARE : RSQUARE { offsetTracker.advanceInLine(1); bracketStack.pop(); };
  
  t_IDENTIFIER : IDENTIFIER { offsetTracker.advanceByTextSize($text); };
  t_NUMBER : NUMBER { offsetTracker.advanceByTextSize($text); };
  
negative.code:   ;
  
  element_list :
       element (element_separator_list element2)*
    ;
  
  element :
       expr_in_array
    ;
  
  element2 :
       expr_in_array2
    ;
  
  //non-empty
  