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}),
);
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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(),
);
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