Tcl uses the proc command to define procedures. Once defined, a Tcl procedure is used just like any of the other built-in Tcl commands. The basic syntax to define a procedure is:
proc name arglist body
The first argument is the name of the procedure being defined. The second argument is a list of parameters to the procedure. The third argument is a command body that is one or more Tcl commands.
The procedure name is case sensitive, and in fact it can contain any characters. Procedure names and variable names do not conflict with each other. As a convention, this book begins procedure names with uppercase letters and it begins variable names with lowercase letters. Good programming style is important as your Tcl scripts get larger. ...