Needless to say, all of this only works if the regex engine satisfies certain assumptions, i.e., order of "evaluation" is guaranteed.
In abstract semantics of regular expressions, a|b and b|a are equivalent.
In abstract semantics of regular expressions, a|b and b|a are equivalent.
"Tarzan" will match one character earlier than Tarzan as the sting is scanned, so it would be discarded even if you flipped the order of the alternation.
This isn't true of examples where the good and bad marches can start at the same character.