Ugliness abounds, but this should do it:

(%baz = %{$_->[0]}), (@bar = @{$_->[1]}) for [&foo()];
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I'm using $_ as a holder for an array ref to the return value.

Hey, it's one line. No, I can't think of a quick idiom, unless you permit global variables:

our (%baz, @bar);
(*baz, *bar) = &foo();
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But mucking with the symbol table is generally bad form as well.

-- Randal L. Schwartz, Perl hacker