When to use perl(:WITH_...) requires?

[Chris Weyl]

Hey all --

Perl provides a number of provides flags, e.g.:

perl(:WITH_ITHREADS)
perl(:WITH_LARGEFILES)
perl(:WITH_PERLIO)
perl(:WITH_THREADS)

Most perl module spec files only deal with perl(:MODULE_COMPAT_5.8.8),
etc.  But I see a number of them (arch-specific, typically), do use
these flags, along the lines of:

Requires: %(perl -MConfig -le 'if (defined $Config{useithreads}) {
print "perl(:WITH_ITHREADS)" } else { print "perl(:WITHOUT_ITHREADS)"
}')

etc, etc.

So, when should I use these?  Should lines along the one above be
included for all flags in an arch-specific spec file?  What's a good
rule of thumb here?

                       -Chris

-- 
Chris Weyl
Ex astris, scientia