+marc('260','b',
+ rec('210','c'),
+);
+
+marc('260','c',
+ rec('210','d'),
+);
+
+# marc_compose('260',
+# 'a', split_rec_on('210','a', qr/\s*;\s*/, 1),
+# 'b', first(rec('210','c')),
+# 'a', split_rec_on('210','a', qr/\s*;\s*/, 2),
+# 'c', first(rec('210','d')),
+# );
+