Major Description
On behalf of Tomas Kukosa:
If the expression contains nested array/map access then the getVariables() method does not return the right value.
The result of test code below is:
script: A+B[C]+D[E[F]]+x[y[z]]
variables: [[A], [C], [B], [D], [x]]
E, F, y, z variables got lost somewhere.