use strict;
use warnings;
BEGIN {
    package Wahoo;
    require Exporter;
    use vars qw[ @ISA @EXPORT_OK $WA $HOO ];
    @ISA = qw[ Exporter ];
    @EXPORT_OK = qw[ $WA $HOO ];
    $WA = $HOO = 0;
    sub Wahoo { $WA = $HOO = 4; }
    $INC{'Wahoo.pm'} = __FILE__;
}

package main;
use Wahoo qw[ $WA $HOO ];
warn "$Wahoo::WA $Wahoo::HOO ";
warn "$WA $HOO ";
Wahoo::Wahoo();
warn "$Wahoo::WA $Wahoo::HOO ";
warn "$WA $HOO ";
__END__
0 0  at - line 16.
0 0  at - line 17.
4 4  at - line 19.
4 4  at - line 20.