As far as I know, when using lvalue subs you are not supposed to explicitly return anything. You just have to gently place the variable you want at the appropriate position and pray to the Perl gods to take it away. If you return it, the whole contract breaks down. Even an if can ruin it, as your variable is stuck in the wrong spot. 
sub assign_to_hash : lvalue
{
     exists($hash{$_[0]})? $hash{$_[0]} : undef;
}

[download]
That should certainly do the trick. If you don't care about assigning to new places, you can simplify: 
sub assign_to_hash : lvalue
{
     exists($hash{$_[0]})? $hash{$_[0]} : $hash{$_[0]} = undef;
}

[download]
It's peculiar, but effective. Just be careful.

In reply to Re: lvalue subs return undef, playing with experimental features, the End of the World, etc by tadman
in thread lvalue subs return undef, playing with experimental features, the End of the World, etc by erikharrison

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