If lookbehinds of unknown length is the sole reason you're looking to upgrade, I probably wouldn't bother. It's the Python regex module used for plugins that allows for that. Not Sigil's PCRE implementation. At least I think that's still the case.
Maintaining two different versions of Sigil simultaneously on the same machine will likely be more trouble than it's worth for the average user. Best case scenario is you make a backup of your 0.7.2 preferences directory so you can reinstall Sigil and restore your old prefs if you need to go back.
|