Based on the instructions in the article (tho I haven't tried it out), putting a semicolon before the hash would work...
proc some_proc {a b} {
} ;# some_proc
That's easier to explain though - you are passing the arguments {a b} { } # and some_proc to the procedure some_proc. Because comments are just another command, the # has to be the first non-whitespace character on the line.