Successfully installed ScriptRunner 2.1.3 into Jira 5.2.2 and I have my managers using versionMatch in the JQL queries -- they were quite happy.
I restarted Jira and then my managers started nagging me that versionMatch could no longer be found. From the Admin page, I selected "Scripted JQL Functions" and scrolled to versionMatch where it indicated it was enabled (i.e. enabled link greyed out and disable link enabled). I pressed the disable and then the enable links, and that resulted in versionMatch function being found and operational.
I really don't want to have to reenable these functions after every restart.