As you're dealing with passwords, I hope you've considered the security implications. If not, please do so.

A little more code than my %pword = (Rich => '', Broke => '',); would have been useful. I'm not sure why you'd consider reversing the hash. You haven't described what problem you're encountering using a username as a key. Here's a few code snippets that might prove helpful:

exists $pword{$username}

Returns TRUE if $username is a key in %pword, FALSE otherwise. See exists.

length $pword{$username}

Returns TRUE if a password has been set (i.e. not the original zero-length value of ''), FALSE otherwise. See length.

$pword{$username}

Returns the current password for $username.

$pword{$username} = $password

Sets a new password for $username.

If you're having fundamental problems with how to handle hashes, take a look at perldata.