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use vars qw( @ISA @EXPORT_OK %EXPORT_TAGS );
BEGIN {
    @ISA = qw( Exporter );
...
    %EXPORT_TAGS = ( ... );  # if necessary
    use Exporter;
}

use vars qw( @EXPORT_OK %EXPORT_TAGS );
BEGIN {
    @EXPORT_OK   = qw( ... );
...
    require Exporter;
    *import = \&Exporter::import;
}