Symbol errors

while searching for arity N function, semantic error: unresolved function call
The script calls a function with N arguments that does not exist. The function may exist with different arity.

semantic error: array locals not supported: $\ldots$
An array operation is present for which no matching global declaration was found. Similar messages appear if an array is used with inconsistent arities.

semantic error: variable 'foo' modified during 'foreach'
The array foo is being modified (being assigned to or deleted from) within an active foreach loop. This invalid operation is also detected within a function called from within the loop.