#testmode:repl

# Non-mutable boolean is copied (issue #70)
a = true
b = a
a += true
a b

# Mutable list is used by reference
l = (1, 2)
l + 3
l
l += 3
l

#---
#(2, true)
#(1, 2, 3)
#(1, 2)
#(1, 2, 3)