S'^(?:(?:(a|\\+)(?!$))(?:(?:/(?:(b|\\+)(?!$)))(?:(?:/(?:c|\\+))|/#)?|/#)?|#)$'
p1
.S'a/#\na/b/c\na/b/+\na/b\na/+\n+\n+/b\n+/+/+\n+/b/c\na/c'
p2
.I8
.S''
.