Terraform

# List of maps
listener = [{
    instance_port = "${var.backend_port}"
    instance_protocol = "${var.backend_protocol}"
    lb_port = 80
    lb_protocol = "http"
  },{
    instance_port = "${var.backend2_port}"
    instance_protocol = "${var.backend2_protocol}"
    lb_port = 8080
    lb_protocol = "http"
}]

# Reference a list
listener = ["${var.elb_listeners}"]

# Map processing example I.
variable "rules" {
  default = {
    "a" = "200,false,tcp,allow,0.0.0.0/0,23,23"
    "b" = "100,true,tcp,allow,0.0.0.0/0,1024,65535"
  }
}

resource "aws_network_acl_rule" "bar" {
  count          = "${length(var.rules)}"
  network_acl_id = "${aws_network_acl.bar.id}"
  rule_number    = "${element(split(",",element(values(var.rules),count.index)),0)}"
  egress         = "${element(split(",",element(values(var.rules),count.index)),1)}"
  protocol       = "${element(split(",",element(values(var.rules),count.index)),2)}"
  rule_action    = "${element(split(",",element(values(var.rules),count.index)),3)}"
  cidr_block     = "${element(split(",",element(values(var.rules),count.index)),4)}"
  from_port      = "${element(split(",",element(values(var.rules),count.index)),5)}"
  to_port        = "${element(split(",",element(values(var.rules),count.index)),6)}"
}

# Map processing example II
variable "rules" {
  default = [
    {
      rule_number = 200
      egress = false
      protocol = "tcp"
      rule_action = "allow"
      cidr_block = "0.0.0.0/0"
      from_port= 23
      to_port = 23
    },
    {
      rule_number = 100
      egress = true
      procotol = "tcp"
      rule_action = "allow"
      cidr_block = "0.0.0.0/0"
      from_port = 1024
      to_port = 65535
    },
  ]
}

resource "aws_network_acl_rule" "bar" {
  count          = "${length(var.rules)}"
  network_acl_id = "<id>"
  rule_number    = "${lookup(var.rules[count.index], "rule_number")}"
  egress         = "${lookup(var.rules[count.index], "egress")}"
  protocol       = "${lookup(var.rules[count.index], "protocol")}"
  rule_action    = "${lookup(var.rules[count.index], "rule_action")}"
  cidr_block     = "${lookup(var.rules[count.index], "cidr_block")}"
  from_port      = "${lookup(var.rules[count.index], "from_port")}"
  to_port        = "${lookup(var.rules[count.index], "to_port")}"
}