# croak on global underscore usage: # no Underscore; # carp on global underscore usage: # no Underscore 'carp'; package Underscore; use Carp (); my $complain = \&Carp::croak; sub TIESCALAR { bless \(my $dummy) => shift } sub FETCH { $complain->("read access to \$_ forbidden") } sub STORE { $complain->("write access to \$_ forbidden") } sub unimport { tie($_, __PACKAGE__); $complain = \&Carp::carp if $_[1] eq 'carp'; } sub import { untie $_ } tie($_, __PACKAGE__) unless tied $_; 1;