modify or delete variable

[Ray Andrews <rayandrews@xxxxxxxxxxx>]

        var=( ${(M)var:#*(#i)$substring*} )
        var=(
      ${var//(#bi)($substring)/aaa${match[1]}bbb )
      
      ... can those to operations be combined?  If a string exists in a
      variable, modify it, else delete it?  I'm betting yes.  Mind,
      there's nothing wrong with two easy to understand steps even if a
      microsecond might be saved by combining them.