use constant DB_ERROR => "database error";
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Okay, misunderstanding. I thought this happens in your code but it is actually a line from the import() sub of constant.

                } else {
                    # Catch-all - what did I miss? If you get this err
+or,
                    # please let me know what your constant's name was
+.
                    # Write to <rootbeer@redcat.com>. Thanks!
                    warnings::warn("Constant name '$name' has unknown 
+problems");
                }
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Your example works here. Perhaps some non-printable characters have sneaked in to your text file or there is a clash (other module or within your code) that uses the same constant? What happens if you change DB_ERROR to MY_DB_ERROR? No better ideas ATM, sorry.

Your suggestion of the potential of unprintables was very astute- I removed the line and carefuly re-typed it. Same warning.

I noticed there were 2 constants defined. I moved the 2nd to the top , and now THAT one throws the warning , but the other is fine. So whichever is first throws a warning!

This makes me wonder- the author doesn't declare:

use constant;
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above these pragmas. maybe that would fix this? I don't see that in the Metacpan but perhaps they're incomplete examples?

APPRECIATE all the kind advice guys- I'll wait for the admin to get my module updated and pray for better results :)