@ADmad Even though I think it's ugly if we let Arrays through, the problem will be PEBCHAK ;-)

But you are right, we don't need so much safeguarding.
What do you think of it now?

Here a list of all related tests (for your convenience):
testBlockSet
testBlockReset
testBlockSetNull
testBlockSetObjectWithToString
testBlockSetObjectWithoutToString
testBlockSetDecimal

testBlockAppend
testBlockAppendNull
testBlockAppendObjectWithToString
testBlockAppendObjectWithoutToString
testBlockAppendDecimal

testBlockPrepend
testBlockPrependNull
testBlockPrependObjectWithToString
testBlockPrependObjectWithoutToString
testBlockPrependDecimal