I'm sure somebody else will come up with something more optimal...

#1. 
if ((scalar grep {defined} values %{$hash}) == 0) {
   # all values are undef
}

#2.
$hash = { map {$_ => undef} keys %{$hash} };
# now empty

[download]

Update: Changed > 0 to == 0, since the poster asked for "check if empty"

Update: Fixed precedence problem (pointed out by original poster). Works now.

In reply to Re: hash problem by crenz
in thread One liner to Check and undef hash elements by Anonymous Monk

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