I need to convert a flat list of keys into a nested hash, as follow:
my $hash = {};
my @array = qw(key1 key2 lastKey Value);
ToNestedHash($hash, @array);
Would do this:
$hash{'key1'}{'key2'}{'lastKey'} = "Value";
sub to_nested_hash {
my $ref = \shift;
my $h = $$ref;
my $value = pop;
$ref = \$$ref->{ $_ } foreach @_;
$$ref = $value;
return $h;
}
Explanation:
We know:
my $h = {}; my $a = [];
).It might be more explicit to do this:
foreach my $key ( @_ ) {
my $lvl = $$ref = {};
$ref = \$lvl->{ $key };
}
But owing to repeated use of these reference idioms, I wrote that line totally as it was and tested it before posting, without error.
As for alternatives, the following version is "easier" (to think up)
sub to_nested_hash {
$_[0] //= {};
my $h = shift;
my $value = pop;
eval '$h'.(join '', map "->{\$_[$i]}", 0..$#_).' = $value';
return $h;
}
But about 6-7 times slower.