->{}
->{
  1
}
->do end
->do
end
->(){}
->() do end

->(a, b; c) { a b }
->(p1, p2, p3 = 3, *ps, p4, k1:, k2: , k3: 3, **ks, &block) {}

-> a { a }
->a, b { b(a) }
-> a, # a
  # b
  b { a + b }

# 0
-> ( # 1
  # 2
  a, # 3
  # 4
  b; # 5
  # 6
  c # 7
  # 8
) { # 9
  # 10
} # 11
# 12

-> { _1 }
-> { [_1, _2] }

-> do
  1
rescue
  2
else
  3
ensure
  4
end