A user reported an error to me that I've seen a few times recently. His code was doing something like this:

Later on he did...

His error said that he was trying to use a boolean as an array. Where did the error come from?

The arrayAppend function, like a few other ColdFusion functions, return true or false, not the changed data structure. Personally I'm not sure why as I don't know a situation where it would return false.

As another reminder - for functions like these you do not need to actually store the result:

But can instead simply use a shorthand statement: