unset [ -fmv ] name ...
       Each named parameter is unset.   Local  parameters  remain  local
       even  if  unset; they appear unset within scope, but the previous
       value will still reappear when the scope ends.

       Individual elements of associative array parameters may be  unset
       by using subscript syntax on name, which should be quoted (or the
       entire  command  prefixed  with  noglob) to protect the subscript
       from filename generation.

       If the -m flag is specified the arguments are taken  as  patterns
       (should be quoted) and all parameters with matching names are un-
       set.   Note  that  this cannot be used when unsetting associative
       array elements, as the subscript will be treated as part  of  the
       pattern.

       The -v flag specifies that name refers to parameters. This is the
       default behaviour.

       unset -f is equivalent to unfunction.