Mine is similar to the op. Telling built ins that take a list where the list ends.
my %broken = (
monday => join q{/}, q{one}, q{two},
tuesday => sprintf q{%s%s}, q{three}, q{four},
);
my %better = (
monday => join(q{/}, q{one}, q{two}),
tuesday => sprintf(q{%s%s}, q{three}, q{four}),
);
Rather than have to remember that parens are needed in this case I tend to use them all the time. If the function's args are on more than one line it gives you something to pin the ; to.
my $str = sprintf(
q{%s -> %s},
get_data(),
get_more(),
);