sub fred { print "FRED>> @_\n" ; }
@fred = qw(a b c) ;

fred() ;
print "ARRAY: @fred\n" ;

my $can = __PACKAGE__->can('fred') ;
print "can1: $can\n" ;

undef_sub('fred') ;

my $can = __PACKAGE__->can('fred') ;
print "can2: $can\n" ;
print "ARRAY: @fred\n" ;

sub undef_sub {
  my $sub = shift ;
  
  my $s = *{$sub}{SCALAR} ;
  my $a = *{$sub}{ARRAY} ;
  my $h = *{$sub}{HASH} ;
  
  undef *{$sub} ;
  
  *{$sub} = $s ;
  *{$sub} = $a ;
  *{$sub} = $h ;
}