Synopsis:
   set input_aliases [on|off|toggle]

Description:
   This setting controls how variables and functions are expanded when used
   directly on the input line.  When turned on, references to them are
   treated as though the command was passed through EVAL; then are expanded
   inline before being passed to the calling command as arguments.

   This setting will not automatically expand items inside parentheses or
   curly braces, however.  The opening brace or parenthesis must be
   quoted with the quote character, '\', for expansion to occur.  Nested
   braces or parenthesis must be double quoted, and so on.

Examples:
   Assuming INPUT_ALIASES is on, $0 is "foo", and $blah is "bar":
      ${[$0]}               expands to "foo"
      ${[$blah]}            expands to "bar"
      ${blah}               expands to "bar", too
      ${ blah == [bar] }    expands to "1"
      ${ [$0] == [foo] }    expands to "1"
      ${ [$0] == [bar] }    expands to "0"
      ${ [$0](booya) }      expands to the return value of $foo(booya)

See Also:
   Expressions(7); Special_Vars(7); eval(5)

Other Notes:
   The behavior of INPUT_ALIASES is different when used inside a loaded
   script.  Variables and functions must use EVAL for inline expansion.
   Instead, this setting causes the standard numeric expandos to return
   the command line arguments used to start the client.