can I define a 'weak' dependency?

[Fulko Hew]

The application I'm packaging is written in Perl, and therefore depends on a
number of Perl modules.
The RPM build successfully detects all dependencies automatically (except
for the ones defined
inside eval() statements).  I have some inside evals so that my code will
'do the right thing'
when executed on MS Windows versus Unix  (These typically entail disabling
features that can't
be supported on Windows.)

Now I'm finding that I would like to have these dependencies (that I have
inside eval()s)
to be included during the installation of the RPM during the yum dependency
resolution
process.  But I know on some distributions (like RHEL) I might not be able
to find a package
(like Chart::Lines), but it _is_ available on Fedora.

Because these dependencies are inside eval()s, I do have to manually define
the
'Requires' statement, but...

Is there anything that I can define in my spec file that would make yum
'try' to resolve
the dependency, but silently fail if it was not found?  Ie. a directive like
'NotMandatoryToRequire'

Ie. Resolve/fetch Chart::Lines when its _is_ available, but be silent about
if it _isn't_ available.

Suggestions?
TIA
Fulko
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.rpm.org/pipermail/rpm-list/attachments/20100712/b4a9cb54/attachment.html>