Synopsis:
   foreach [-]<structure> <variable> { <action> }

Description:
   The FOREACH command is a loop type that iterates through the items in
   a variable (or alias, see below) structure.  This is often useful for
   purging an entire structure, or for searching through it for a certain
   piece of data.

   Variables in the action field are normally not expanded until actual
   execution of the action.  They can be forced to expand early by quoting
   the opening curly brace with a backslash: \{

   If a hyphen (-) is prepended to the structure name, the FOREACH loop
   will try to iterate through an alias structure instead of a variable
   structure.  This is primarily useful for purging alias structures.

Examples:
   Simple usage of FOREACH, assuming $blah is a structure two levels deep:
      foreach blah xx {
         foreach blah.${xx} yy {
            echo $blah[$xx][$yy]
         }
      }

   To purge an alias structure called booya:
      foreach -booya xx {
         alias -booya[$xx]
      }

See Also:
   fe(5); fec(5); until(5); while(5)

Restrictions:
   Structures may be referenced as either $var.${subvar}.${subvar} or
   $var[$subvar][$subvar] (with any number structure levels, of course).
   The notation $var.$subvar.$subvar parses as $var[${subvar.$subvar}],
   which of course is incorrect, and should not be used.

Other Notes:
   The action portion does not necessarily need to do anything, though there
   isn't much point in using the command without it.