This Firebot setup adds a giveaway command that works with subcommands.
!giveaway - Describes what will be given away.
!giveaway start - Clears the file and opens the giveaway.
!giveaway enter - Enter the giveaway, adds username to the list.
!giveaway leave - Leave the giveaway, removes username from the list.
!giveaway close - Closes the giveaway to prevent users from entering.
!giveaway open - Opens the giveaway without clearing the file.
!giveaway draw - Draws a winner from the file.
!giveaway clear - Clears the file.
!giveaway [anything] - A fallback command in case users write a message after the command, it will display the regular !giveaway message.
Find the download here.