Returns information about the stage. A limited number of parameters are supported.

Format: StageVar(param_name) [oper] "string"

Arguments:

- param_name (string): The name of the stage parameter to check. Valid values are: info.name, info.displayname, info.authorname.
- [oper]: =, != (other operators not valid)
- "string" (string): String to compare against. Must be in double quotes.

Return type: boolean (1 if true or 0 if false)

Error conditions: none

Details:

info.author: Compares the value of the "author" parameter in the [Info] group.

info.displayname: Compares the value of the "displayname" parameter in the [Info] group.

info.name: Compares the value of the "name" parameter in the [Info] group.

Example:

`trigger1 = StageVar(info.author) = "Suika"
; Returns true if the stage author is named "Suika".`