I noticed the $.
The environment in question has used the "/" in group names with AIX and Linux
for 2 decades without incident. It also worked with other proprietary Unix platforms.
(But they're all decommissioned now)
They enforced a rule that all group names had to start with an alpha. Then
[[:alnum:][./_-]]
Did a forensic analysis of the existing groups and there's no occurrence of double
punctuation.
(I'm also considering double punctuation such as '..' for '/'
Current plan is to use IdM basically a managed RDHS and Kerberos hub.