http://core.tcl.tk/tcllib/doc/trunk/embedded/www/tcllib/files/modules/control/control.html
no-op is available via the tcllib control structure module.
AMG: I'm not sure if this is how tcllib's no-op is implemented, but it can be done very simply:
proc no-op {args} {}I believe the bytecode compiler specially recognizes and optimizes this.
GraemeP: That is how tcllib does it. There is a discussion on interp alias about creating a no-op, and a command that just returns its args.