如果其值为“undef”，则删除散列元素

Question

I have seen delete that deletes a hash element. But what if some of the elements dates have undef for a value?

I would like to delete all hash elements whose value is undef .

How would I do that in a single line, or the simplest way.

Answer 1

I suggest that you delete a hash slice, using grep to determine which keys correspond to an undefined value

use strict;
use warnings 'all';

my %h = (
    a => 1,
    b => undef,
    c => 1,
    d => undef,
);

delete @h{ grep { not defined $h{$_} } keys %h };

use Data::Dump;
dd \%h;

output

{ a => 1, c => 1 }

Answer 2

foreach (keys %hash) {
    delete $hash->{$_} unless defined $hash->{$_};
}