Beside the effect of allowing bare words (things that look like an identifier) on its left hand side, a fat arrow has no semantic or syntax difference with a comma. It looks different.

Some people use it to separate function arguments that play different roles, a subset of those only after the first argument. For instance, in (s)printf, the first argument (if there's no file handle argument) is a format, the rest a list. Writing

    printf $format => $arg1, $arg2, $arg3;
[download]

emphasis the fact the first argument is "special".

It's a matter of style. Use it if you like it, don't use it if you don't.