This variable identifies whether or not the tcl interpreter is operating in interactive mode or not. If its value is 1 , then the interpreter acts as if it were an interactive interpreter. See tclsh for a list of the differences between interactive and non-interactive mode.
Ro You can shorten commands in interactive mode, e.g.: "inf" for "info".
RS 2004-03-24 Yup - and this is especially delightful on a PocketPC where less stylus-tapping is better. If the abbreviation is unambiguous, like ll for llength, it saves time and screen space; if it is ambiguous (e.g. 'l'), it is another introspection helper - the educational error message shows you the possible completions, just as [info command l*] would have done.
% l ambiguous command name "l": label labelframe ladd lappend ldiff lexpr lframe lindex linsert list list:add list:clear list:filter list:popup list:show listbox ljtext llength lmap lmirrorx load loadvfs loop lower lpop lpush lradio lrange lreplace lrevert ls lsearch lset lsort lspread lsuniq lswap luniq % ll wrong # args: should be "llength list"
Just make sure that the interactive command is tried at global level (0), so that unknown (which provides abbreviation mode) finds itself at level 1.