Complex sentence: The player does not need to play with that perk to raise its level; for example, the Field Medic perk requires the player to heal a number of points to level up, but this can also be done while playing any of the other perks.
Split into simpler sentences: The player does not need to play with that perk to raise its level. For example, the Field Medic perk requires the player to heal a number of points to level up, but this can also be done while playing any of the other perks.