Translations:Expression Manager/44/en
From LimeSurvey Manual
As you can see, anything in curly braces is treated as an expression, so is syntax-highlighted (color coded) in the prior image. If you had any typos (such as misspelled or undefined variable names or functions), EM would show an error, such as this, showing that height_unit is an undefined variable name (it is actually height_units), and rnd() is an undefined function (the proper function name is round()). In both cases, the errors are surrounded by a red box to make it easier to spot and fix them.