Cannot use -f with source file from stdin

[RussellSprouts]

I have a long series of commands I'd like to run on some BUILD file text. The commands sometimes have different targets, so I can't pass the commands on the commandline. I tried writing my commands to a temp file, and then using -f. In the file, I use -:__pkg__ to operate on stdin. However, I get this error:

-/BUILD: file not found or not readable

It seems that - is not recognized in a command file.