Which Dancer environment are you running in? "development" or "production"? Check the corresponding file in enviroments/ for the value of auto_reload. It should be 0, but the "attempt to reload" makes me suspect that it may be enabled.

As for why it's happening, my theory would be that your program works fine the first time it's run in a specific apache child process, but then subsequent requests to the same child (presumably incorrectly) detect that unite.pm has changed and attempt to reload it, which fails. But that's just a half-assed theory since the details of your situation are a little sparse.