What would be the approach if the string were an octet string? I came across more genius documentation for a different OID:
A string of octets containing one bit per VLAN in the
management domain on this trunk port. The first octet
corresponds to VLANs with VlanIndex values of 0 through 7;
the second octet to VLANs 8 through 15; etc. The most
significant bit of each octet corresponds to the lowest
value VlanIndex in that octet. If the bit corresponding to
a VLAN is set to '1', then the local system is enabled for
sending and receiving frames on that VLAN; if the bit is set
to '0', then the system is disabled from sending and
receiving frames on that VLAN.
GrandFather has a great example in a post, Re: Convert SNMP Octet String to Array, to convert the octet string, but I don't think I understand how the ranges were created from the bit number. Using GrandFather's example I can convert the string properly, but I can't figure out how to show the VLANs in the range format (1-10,15,20-30, etc).