I'm trying to do something like the following:
<If "%{IPV6} == 'off'">
Header always set Attention "you are using still using IPV4 in %{TIME_YEAR}, please blahblah etc"
</If>
(please withhold commentary regarding the viability of communicating with humans through HTTP headers)
without the %{TIME_YEAR}
it works fine but with it it gives an error Unrecognized header format %,
removing the % just results in the literal string {TIME_YEAR}
being returned in the header
I've tried using expr=%{TIME_YEAR}
or %{env:TIME_YEAR}
but they error out as well
I've tried adding PassEnv TIME_YEAR
prior but it gives an error AH01506: PassEnv variable TIME_YEAR was undefined
TIME_YEAR should be a valid variable according to this: https://httpd.apache.org/docs/2.4/expr.html
I noticed that some variable on that page are tagged as "(not available during <If>
)" but there's no such designation on the time variables
I am using Apache 2.4.41 which (as far as I can tell) should be sufficient to have all of this functionality.