Two things: if that is exactly what your code says, then you're missing a package declaration. Also you can't use my there. Should be our

    package Book::Reader;
    use strict;
    use Exporter;
    our @ISA = qw/ Exporter /;
    our @EXPORT = qw/ getData /;

    ....
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Incidentally, the Expoter bit doesn't mean anything if you are calling your sub with a fully qualified name like Book::Reader::getData(), so if you don't need to export it, you should get rid of those lines...