$ perl -Mstrict -Mwarnings -E ' my %x; say scalar keys %x; say scalar values %x; my %y = (); say scalar keys %y; say scalar values %y; ' 0 0 0 0 #### #!/usr/bin/env perl use strict; use warnings; use Benchmark qw{cmpthese}; cmpthese -1 => { no_assignment => sub { my %hash }, assignment => sub { my %hash = () }, }; #### Rate assignment no_assignment assignment 6672755/s -- -60% no_assignment 16770827/s 151% --