Changing keys in a “for ( keys %hash ) {}”-loop

Question

I remember something about not changing the keys in a

for my $key ( keys %hash ) { ...

for example

for my $key ( keys %hash         


        

Answer 1

See the keys function manpage:

The returned values are copies of the original keys in the hash, so modifying them will not affect the original hash. Compare "values".

You can delete or change hash elements by subscripting, e.g.

delete $hash{$key};
$hash{$key} = "foo";