tabs in configure.in?

[Lars Hecking]

 I couldn't find this in the manual, or with a quick glance through my
 list archive: are there any rules about the usage of tabs in configure.in?
 I just came across some configure.in code that fails if used with tabs.

 Personally, I'd consider it best practice to avoid tabs, but are there
 any hard-set rules I can point other authors to?

 Thanks.