See use for details. In short, during the compilation phase, Perl checks whether Log::Log4perl is already in %INC, if not, it searches @INC for it (Log/Log4perl.pm), compiles it (if the module returns a true value, the compilation phase continues, otherwise it stops), and calls its import with 'get_logger' as an argument. It usually imports the get_logger subroutine to the caller's namespace.

BTW, a semicolon is missing at the end of the line.