But that has a certain ugliness (smell ?) to it, and was looking for a prettier, more aromatic solution.

Yet that's what you're saying you want to do. You could cover the smell with an alias, but there's no avoiding passing the variable by reference if you want to pass the variable by reference.

Update: Here's a simple way of doing it:

sub fill_hashref{
   my $lref = $_[0] //= {};
   $lref->{RETURNVALUE}="I would like to see this";
}
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