is an expression parser. You use it via the "expr" markup, thusly:

   (:if expr equal {$var1} {$var2} xor equal {$var3} {$var4}) 

   (:if expr ! equal 'carrot' {$var4}) 

Operations available are:

  • and
  • or
  • xor
  • &&
  • ||
  • !

I think you can also use parenthetical expressions like

(: if expr ({$bool1} or {$bool2}) and ({$bool3} or {$bool4}) :)

Usage examples here:

This page may have a more recent version on PmWiki:CondExpr, and a talk page: PmWiki:CondExpr-Talk?.