Hi, @alan-kilborn and All,
Yes, these two drop-down lists help us to compare if a specific functionality is supported or not, between two regex engine flavours, as well as some specificities for each one !
Note that my last sentence, between parentheses ( $0 vs $1 ) is not connected at all, with these two drop-down lists, but, simply, refers to subjects asked by @glossar !
BR
guy038