Add a string to an Access Policy variable

In my access policy I have the following variable set up:

session.ldap.last.attr.trimmedMembership = regexp -inline -all {CN=aPUMA[^,]+,} [mcget {session.ldap.last.attr.memberOf}]

This produces the example list depending on the user's LDAP group membership:

CN=aPUMAApp-Admin, CN=aPUMAApp-User, CN=aPUMAWeb-Admin, CN=aPUMASWeb-User

I want to add a new role, aPUMAApp-Design, to the list regardless of the user's group membership.

How do I modify the variable above to do this?