Sure. Here's some short code for you:

while (<IN>) {
  chomp;
  my ($name) = /([^:]+)/;
  @{ $users{$name} }{ @fields } = split /:/;
}
[download]

I basically create the hash reference and assign to it all at once.

---

update: down with temporary variables, up with one-liners.

chomp(@{$users{(/([^:]+)/)[0]}}{@fields} = split /:/) while <IN>;
[download]

japhy -- Perl and Regex Hacker