Without reading all of the code you posted: Do you get any error messages if you use strict (not only in your module, also in the main script), or turn on DBI's RaiseError?

no warnings qw(uninitialized redefine once);
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You should not turn off warnings if looking for errors. Is it necessary to use no warnings in your module? It is probably safer to include a few more lines of code to check for undefined values and these things in the places where this can happen. The extra effort needed to code so that your program runs without warnings pays off in reduced debugging time.