Have a class with 2 spelllist, 1 standard and one custom.
Have a spell on both spelllists but on different levels. i.e. tongues as a 4th level spell on the cleric list and as a 3rd level spell on the my_cleric list. This spell will now show up on the 3rd and 4th level spelllist, as expected.
Make a character that can cast this spell from one spelllist but not the other due to his level. Both spells will show up on the spelllist, the highest as the sole spell on the higher level spell.
CLASS: my_cleric SPELLLIST:cleric,my_cleric
Make a character with classlevels in my_cleric until it has access to 3rd level spells, no higher. The spelllist will now show all 1st, 2nd and 3rd level spells, inlcuding tongues. It will also show a 4th level spelllist with only one spell on it, tongues.