It may be worth moving to the more robust version of GetOptions that takes a hash reference as a first argument. For example:

my %opts;
GetOptions(\%opts, 'user=s', 'pass=s', 'config=s');
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This will store your options in the hash, and you can test whether anything came through with:

usage() unless keys %opts;
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I'd recommend this version for use in most cases actually; it seems cleaner to me than a whole list of arguments to scalar references.