Continuation handling
Code segments (sequences).
Exception types
Function closures and calls
Get the type of the value on the top of the stack as an integer.
Lookup named variable in the environment
Make a new exception object from a string object and push it on the stack
Type aliases for code sequences and names
Push empty value / machine exception / type value onto the stack.
Raise the exception on the top of the stack
Type values
Base class for SECD values.
Attribute mechanism for automatically numbering bytecode instructions