NAME
     switch - Evaluate one of several  scripts,  depending  on  a
     given value

SYNOPSIS
     switch ?options? string pattern body ?pattern body ...?

     switch ?options? string {pattern body ?pattern body ...?}


DESCRIPTION
     The switch command matches its string argument against  each
     of  the  pattern  arguments in order.  As soon as it finds a
     pattern that matches string it evaluates the following  body
     argument  by  passing  it recursively to the Tcl interpreter
     and returns the result of that evaluation.  If the last pat-
     tern  argument  is  default then it matches anything.  If no
     pattern argument matches string and  no  default  is  given,
     then the switch command returns an empty string.

     If the initial arguments to switch start with  -  then  they
     are treated as options.  The following options are currently
     supported:

     -exact    Use exact matching when comparing string to a pat-
               tern.  This is the default.

     -glob     When matching string to the  patterns,  use  glob-
               style  matching  (i.e.  the same as implemented by
               the string match command).

     -regexp   When matching string to the patterns, use  regular
               expression matching (as described in the re_syntax
               reference page).

     --        Marks the end of options.  The argument  following
               this  one  will  be  treated  as string even if it
               starts with a -.

     Two syntaxes are provided for the  pattern  and  body  argu-
     ments.   The  first uses a separate argument for each of the
     patterns and commands; this form is convenient if  substitu-
     tions  are desired on some of the patterns or commands.  The
     second form places all of the patterns and commands together
     into  a  single argument; the argument must have proper list
     structure, with the elements of the list being the  patterns
     and  commands.   The  second form makes it easy to construct
     multi-line switch commands,  since  the  braces  around  the
     whole list make it unnecessary to include a backslash at the
     end of each line.  Since the pattern arguments are in braces
     in the second form, no command or variable substitutions are
     performed on them;  this makes the behavior  of  the  second
     form different than the first form in some cases.

     If a body is specified as ``-'' it means that the  body  for
     the  next  pattern  should also be used as the body for this
     pattern (if the next pattern also has a body of  ``-''  then
     the body after that is used, and so on).  This feature makes
     it possible to share a single body among several patterns.

     Beware of how you place comments in switch  commands.   Com-
     ments should only be placed inside the execution body of one
     of the patterns, and not intermingled with the patterns.

     Below are some examples of switch commands:
          switch abc a - b {format 1} abc {format 2} default {format 3}
     will return 2,
          switch -regexp aaab {
            ^a.*b$ -
            b {format 1}
            a* {format 2}
            default {format 3}
          }
     will return 1, and
          switch xyz {
            a
               -
            b
               {
               # Correct Comment Placement
               format 1
            }
            a*
               {format 2}
            default
               {format 3}
          }
     will return 3.


SEE ALSO
     for(n), if(n), regexp(n)


KEYWORDS
     switch, match, regular expression