Also note that the
mariadb_read_default_file is equivalent to
--defaults-file, not
--defaults-extra-file (but it probably doesn't matter in the context of the question). See
Custom Option File Locations.
map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]