That's silly. Someone who doesn't know what join does or the arguments it takes--or who doesn't know how to look it up in a reference or in the Perl documentation--has no business maintaining a serious Perl program. While there are definitely Perl operators with poor interfaces (caller is one of my least favorite), avoiding the use of join and slices because people who don't know Perl might not understand it is silly.

(I realize you said "casual reader", which implies someone not reading carefully, but a similar argument applies there.)