Question

I’m looking for a nice way to sort a hash in Perl by value first and by key afterwards.

Example:

 my %userids = (
  williams => "Marketing",
  smith    => "Research",
  johnson  => "Research",
  jones    => "Marketing",
  brown    => "Marketing",
  davis    => "Research"
);

Output:

Marketing: brown
Marketing: jones
Marketing: williams
Research: davis
Research: johnson
Research: smith

Please note that value was the first sorting level. Second sorting level is key. Any idea how to do this in an elegant and high-performance way? Thanks!

Answer 1

Good reference: http://www.misc-perl-info.com/perl-sort.html#shv

#!/usr/bin/perl

my %userids = (
    williams => "Marketing",
    smith    => "Research",
    johnson  => "Research",
    jones    => "Marketing",
    brown    => "Marketing",
    davis    => "Research"
);

foreach (sort { ($userids{$a} cmp $userids{$b}) || ($a cmp $b) } keys %userids) 
{
    print "$_: $userids{$_}\n";
}