main.tf

terraform {
  required_version = ">= 0.14.9"
}

variable "random" {
  type = number
}

module "my_animal_module" {
  source = "./my-animal-module"
  random = var.random
  gtr = 7
  species_if = "monkey"
}

my-animal-module.tf

variable species {
  default = "horse"
}

variable gtr {
  type = number
}

variable species_if {
  type = string
}

variable random {
  type = number
}

resource "local_file" "animal" {
  content = var.random > var.gtr ? var.species_if : var.species
  filename = "./animal.txt"
}