Can you have the package read __DATA__ and fill a package variable, if the package variable isn't defined yet? Something like:

{
    my %config;
    sub new {
        if (not %config) {
            %config = read_config_from(__DATA__);
        }
        # Now create the object...
    }
}
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I'm sure you could make this more flexible, reading from __DATA__ unless passed some other file or file handle.

2019-04-11 Athanasius fixed opening code tags