labelcas – Check the existence of labels, and fork accordingly

The pack­age de­fines two com­mands: – \each­la­bel­case, which dis­tin­guishes whether a set of la­bels is de­fined, and for each la­bel ei­ther queues ac­tion ac­cord­ingly, or ap­pends the ac­tion to a macro; and – \lot­la­bel­case, which takes a comma-sep­a­rated list of la­bel names, and dis­tin­guishes the re­sult­ing ac­tion on whether all were de­fined, whether none were de­fined, whether not all were de­fined, or whether the lest is empty (again, the ac­tion re­sult­ing from \lot­la­bel­case may be writ­ten to a macro).