Perl: Delete keys in hash that don't exist as elements in array -

i have array of key names , need remove keys not in list hash.

i gather deleting keys in hash bad thing while iterating on it, seem work:

use strict; use warnings; use data::dumper;  @array=('item1', 'item3'); %hash=(item1 => 'test 1', item2 => 'test 2', items3 => 'test 3', item4 => 'test 4');  print(dumper(\%hash));  foreach (keys %hash) {     delete $hash{$_} unless $_ ~~ @array; }      print(dumper(\%hash)); 

gives output:

$var1 = {       'item3' => 'test 3',       'item1' => 'test 1',       'item2' => 'test 2',       'item4' => 'test 4'     }; $var1 = {       'item3' => 'test 3',       'item1' => 'test 1'     }; 

can explain me better/cleaner/safer way of doing this?

many thanks.

don't use smartmatch ~~, it's fundamentally broken , removed or substantially changed in upcoming releases of perl.

the easiest solution build new hash containing elements you're interested in:

my %old_hash = (     item1 => 'test 1',     item2 => 'test 2',     item3 => 'test 3',     item4 => 'test 4', ); @keys = qw/item1 item3/;  %new_hash; @new_hash{@keys} = @old_hash{@keys};  # uses "hash slice" 

if want update original hash, %old_hash = %new_hash afterwards. if don't want use hash, might use list::moreutils qw/zip/:

# unfortunately, "zip" uses idiotic "prototype", override # calling "&zip(...)" %hash = &zip(\@keys, [@hash{@keys}]); 

which has same effect.