Tcl uses the pound character, #, for comments. Unlike in many other languages, the # must occur at the beginning of a command. A # that occurs elsewhere is not treated specially. An easy trick to append a comment to the end of a command is to precede the # with a semicolon to terminate the previous command:
# Here are some parameters set rate 7.0 ;# The interest rate set months 60 ;# The loan term
One subtle effect to watch for is that a backslash effectively continues a comment line onto the next line of the script. In addition, a semicolon inside a comment is not significant. Only a newline terminates comments:
# Here is the start of a Tcl comment \ and some more of it; still in the comment
The behavior of a backslash in comments ...