N -- new feature -- I may consider using it
B -- breaking change -- I should review my code
N def-expr now returns the symbol of its name instead of nil.
N Array#to_h converts an array of key-value pairs into a Hash.
N Enumerable#to_h converts a list of key-value pairs into a Hash.
N Binding#local_variable_get(symbol)
N Exception#cause provides the previous exception which has been caught at where raising the new exception.