in reply to Silencing warnings when testing
If you use Test::More, you can use the diag() function to print diagnostic or debugging information. Test::Harness will suppress it when running tests normally. You can run the test by hand or with the verbose flag and see them.
If you are using Test::More, you can also use Test::Exception and Test::Warning to test for death and warnings. I've had good results with them.
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Seekers of Perl Wisdom