Special name for an argument to a [proc] - if it's last in the argument list, it will contain a list (possibly empty) of all the remaining arguments. '''example args''' Class Club -parameter {id {name unknown}} Class Player -superclass Club -parameter {{name unknown} {position unknown}} Player proc show_players '''args''' { if { [string length $args] == 0} { puts "Show players DB" foreach p [my info instances] { puts "[$p name] [$p position]" } return } set pos [string toupper $args] puts "Players with postition $pos:" foreach p [my info instances] { foreach char [split $pos {}] { if {[string first $char [$p position]] == 1} { puts "[$p name] [$p position]" break } } } } ---- Is it just me, or is that a pretty poor example of args? for one, it uses rather unconventional quoting (what's with all the single quotes?). Second, you do [string length $args] and [string toupper $args] but you firmly established that args is a list, not a string. It is generally accepted as bad practice to perform string operations on lists.