TitleJoin is a simple awesome plugin to provide a nice, warm welcoming to new players and players that have played before.
On the join of a player, if he has played before, "MessageTitle" would be ran and it would run the line of code you provided. For example, "Welcome back, &b&player%" would show a text in the middle of their screen saying "Welcome Back, &bExusKun" (The person who joins will see their name).
enable-subtitle-welcome & enable-subtitle-welcomeback are both the under text of the title, so if welcomeback was "true", it would show this:
and if it is "false", it would show this:
Sorry for the sloppy showcase, I will improve it a bit later after I've updated a couple of other plugins