my $other_secret = Crypt::SecretBuffer->new("Foo");
$password->unmask_secret_to(\&do_something, $user, $password, $other_secret);

##</code><code>##

my $other_secret = Crypt::SecretBuffer->new("Foo");
$password->unmask_to(sub($pass) { do_something($user, $pass, $other_secret) });

##</code><code>##

use 5.036;

*unmask_secrets_to =
    eval { require Crypt::SecretBuffer; \&Crypt::SecretBuffer::unmask_secrets_to }
    || sub($cb, @args) { &$cb(@args) }
;

sub private_fn {
    say "@_";
}

sub my_api_function($user, $password, $secret) {
    unmask_secrets_to(\&private_fn, $user, $password, $secret);
}