perhaps with the exception of :lvalue subs, haven't tried those

lvalue subs are called in scalar context, so they can't return a list.

use strict;
use warnings;
my ($i,$j);
sub f :lvalue { ($i,$j) }
f() = (4,5);
print("$i,$j\n");
[download]

Useless use of a constant in void context at script.pl line 5.
Use of uninitialized value in concatenation (.) or string at script.pl
+ line 6.
,5
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Wrong. Don't forget that plain = is the scalar assignment operator, unless there is a hash or array on the left. ()= is the list assignment operator:

$ perl
use strict;
use warnings;
my ($i,$j);
sub f :lvalue { ($i,$j) }
(f()) = (4,5);
print("$i,$j\n");
__END__
4,5
[download]

However, I would be very leery of using a relatively new feature like that that has probably not been used much in that way.
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Ah thanks, (although, not just "()=" is the list assignment operator).

I would be very leery of using lvalue subs *in any way*.

Which relative new feature are you refering to? lvalue subs have been around since at least 5.6.0, and maybe even before that.