Expands to:

render previews what an expanded dependency block expanded to

With the block-iteration experiment enabled, a dependency block that carries an expansion block now renders as it was written, followed by the elements it expanded into, commented out and with their bodies resolved:

$ terragrunt render --experiment block-iteration
dependency "aurora" {
  expansion {
    for_each = toset(["web", "api"])
  }

  config_path = "../aurora-${each.key}"
}

# Expands to:
#
# dependency "aurora" {
#   config_path = "../aurora-api"
# }
#
# dependency "aurora" {
#   config_path = "../aurora-web"
# }

The elements are comments because they aren't valid Terragrunt HCL configurations (you are not allowed to use the same dependency label twice in Terragrunt configurations), the previews are there to help you understand how expansion will resolve.