Nope, it is Perl's "Do What I Mean" magic.
But seriously, in the docs of Dancer::Plugin::Database I read:
AUTOMATIC UTF-8 SUPPORT
As of version 1.20, if your application is configured to use UTF-8 (you've defined the charset setting in your app config as UTF-8) then support for UTF-8 for the database connection will be enabled, if we know how to do so for the database driver in use.
If you do not want this behaviour, set auto_utf8 to a false value when providing the connection details.
So indeed don't do anything other than enabling UTF-8 in your configuration and don't mess around with setting UTF-8 yourself.
DWIMMERY at its best.
A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James
My blog: Imperial Deltronics