fmt can contain any string. Instances of j are replaced with the input Japanese, r with the rōmaji, and l with the lit. translation. If l is not used and there is a lit. translation given then it always goes after either the Japanese or rōmaji, whichever is used second (although both would be required).
Spacing is ignored and handled automatically. To preserve spacing and to print "j", "r", or "l" characters, square brackets can be used and their contents remain. Square brackets can be printed literally inside of square brackets, however the "j", "r", and "l" values cannot appear inside them.