I think use warnings; and use strict; would go a long way toward solving this for you. You call your arrayref $user sometimes, and some of those may be in the code.

The last index of $users will be in $#$users, not $$#users. Observe,

$ perl -Mstrict -we'my $foo = ["a".."z"];print $#$foo,$/'
25
$ perl -Mstrict -we'my $foo = ["a".."z"];print $$#foo,$/'
14354
$
[download]

I'm not entirely sure what $$#users represents, but that explains your extra array elements.

I'm leery of your hash keyed to surname. When you insert Minnie, Mickey will get clobbered.