I've been having a lot of problems lately with "Unknown Error" getting reported rather than the actual error message. Since it started at roughly the time I upgraded to 5.10, I figured it was some strange 5.10/OS X issue, and since it was occurring in a project that has a gigantic code base, it took me a while to track it down. Turns out it's actually something related to namespace::clean that is causing the problem.

I've managed to narrow it down to this minimal test case, but I haven't had any luck in figuring out why this is occuring...

package Test1;
use namespace::clean;
sub foo { if } # Yes, this is an intentional syntax error
1;
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I'm simply running this code from the command line like so:

% perl -Ilib -MTest1 -e1
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If you remove the call to 'use namespace::clean', this is the output (which is what I would expect)

syntax error at lib/Test1.pm line 2, near "if }"
Compilation failed in require.
BEGIN failed--compilation aborted.
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However, when using namespace::clean, the output becomes:

Unknown error
Compilation failed in require.
BEGIN failed--compilation aborted.
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Obviously this makes it very difficult to find bugs when it isn't even reporting which file the error was in when loading up hundreds of modules for a very large application. I realize namespace::clean is doing some pretty heavy magic, but I'd hate to give it up considering how tremendously useful it is.

Update:

Reported it to RT (43362). I also forked it on github and added a testcase (http://github.com/jasonk/namespace-clean).