Missing tcl command?

I’m using OpenOCD 0.10.0 on OSX (via homebrew). I’m trying to use an MCU script file for the rtl8710 and I’m getting an unknown command error in:

set size [file size $local_filename]

“file size” seems to be a valid jim-tcl command. Am I missing something?

It is working fine with Linux (using last git master branch).

Maybe this is something broken on OSX only.