FORGET is available since version 1.0.0.
Removes a symbol from the symbol table.
// Store a value in 'a'
41 'a' STORE
// Forget the value
// Conditionally store a new value in 'a'
42 'a' CSTORE
// Notice that 'a' was indeed set by 'CSTORE' and thus was not in the symbol table after the 'FORGET' call