The currently released Grid (on Curse) supports LHC3. The alpha (available here) supports LHC4. This support went into r1218 on 2009-10-22.
If you tried this a few months ago, you probably did it before support went in.
LHC3 and LHC4 cannot directly communicate with each other. LibWrapperHealComm-1.0 exists for this purpose. Most addons that support LHC4 also include this, but it appears that X-Perl does not. For X-Perl to send and receive LHC3 data, therefore, you need another mod installed that loads LWHC. Try VisualHeal.
Edit: Alternately, install LibWrapperHealComm-1.0 just as you do for LibHealComm-4.0.
I don't use X-Perl, so I can't speak for the configuration. I don't believe it requires any, though.
1. Download LibHealComm 4.0
2. Unzip and put the folder in your Addons folder.
3. Log into World of Warcraft
4. Done. Now you should see all incoming heals from people using the mod, and they should see mine.
Thanks for whoever can help me out.
It should show predictive heal amounts in some fashion.
Looked at the latest version of X-Perl and it only mentions LibHealComm 3.0. I'm assuming it only supports 3.0 right now?
X-Perl supports both, preferring LHC4. However, it appears that the .toc lists LHC3 as an optional dependency, but not LCH4. This is a bug. If you're running on an alphabetical file system, this likely won't affect you.
Grid does include LWHC, so yes.