One thing I'd like to add is that returning a hash reference allows for beatiful syntax when you're using a single element from it.

sub hash    {   qw(foo bar baz xyzzy)   }
sub hashref { { qw(foo bar baz xyzzy) } }
my $dummy;

# Using a single element only

$dummy = ${ hash }{foo}; # UGLY!

$dummy = hashref->{foo}; # Neat!

# or     hashref()->{foo}
# or     hashref->{'foo'}
# etcetera.
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But in the end, it's all up to you. Be sure to document your choise!

Originally posted as a Categorized Answer.