in reply to Re^4: Effecicncy of key-only hash
in thread Effecicncy of key-only hash

Then (according to all benchmarks here) you should go with undefining the hash slice (undef @h{qw{a b c d}}).
[]s, HTH, Massa (κς,πμ,πλ)

In Section Seekers of Perl Wisdom