See Slices.
Also, it's faster than assigning the keys one by one, as the loop runs in C rather than Perl.
#!/usr/bin/perl
use warnings;
use strict;
my @keys = 'a' .. 'z';
sub one_by_one {
my %hash;
undef $hash{$_} for @keys;
}
sub slice {
my %hash;
@hash{@keys} = ();
}
use Benchmark qw{ cmpthese };
cmpthese(-3, {
one_by_one => \&one_by_one,
slice => \&slice,
});
__END__
Rate one_by_one slice
one_by_one 267946/s -- -25%
slice 359541/s 34% --
map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]
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