Quoting Dean Brooks:
> For example, the following (made-up) example will generate an error
> with Exim 4.65 where it worked fine previously:
...
> deny condition = ${if >{$acl_m0}{0}}
As $acl_* is empty by default (unless strict_acl_vars is set, as of
4.64), you should use ${if !def:acl_m0}.
While I agree that a minor version step is not the right time to
introduce such a change in behaviour, I really don't think Exim should
allow (and thereby encourage) all kinds of poor configuration habits.
I propose to make the "empty string in numeric comparison" behaviour
configurable (like strict_acl_vars, or in Perl speak "use strict", which
I use even for the most simple script btw), defaulting to "not strict".
People will then have time to sanitize their config and enable the
strict mode eventually (assuming they care about reliable operation).
