[ownedbycats]

While trying to set up the template in #530 I found a failure point that I'm surprised I managed to miss:

program:

	if 
		!$#purchasesource=="Amazon"
		&& select($identifier, 'amazon')
	then
		list_difference ($identifier, strcat('amazon:', select($identifier, 'amazon')), ',')

	elif 
		!$#purchasesource=="Barnes & Noble"
		&& select($identifier, 'barnesnoble')
	then
		list_difference ($identifier, strcat('barnesnoble:', select($identifier, 'barnesnoble')), ',')

	elif 
		!$#purchasesource=="Kobo"
		&& select($identifier, 'kobo')
	then
		list_difference ($identifier, strcat('kobo:', select($identifier, 'kobo')), ',')
	
	elif 
		!$#purchasesource=="Baen"
		&& select($identifier, 'baen')
	then
		list_difference ($identifier, strcat('baen:', select($identifier, 'baen')), ',')
	fi

If it finds one unwanted identifier, it would then skip the rest. What should I use instead of if-thens?