Terraform 0.12 - merge and output map values based on key

0_variables.tf

variable "var_a" {
    type = "map"
    default = {
        "a" = "one"
        "b" = "two"
    }
}

variable "var_b" {
    type = "map"
    default = {
        "a" = "one"
        "b" = "two"
    }
}

1_example.tf

# Handles matches where B does not have the key listed in A
output "my_vars_mismatch" {
  value = {
      for item in keys(var.var_a):
      var.var_a[item] => lookup(var.var_b, item, null)
  }
}

2_example.tf

# Assumes that the lists are aligned
output "my_vars_aligned" {
  value = {
      for item in keys(var.var_a):
      var.var_a[item] => var.var_b[item]
  }
}