What you want to do is accept a parameter input as the name of an arbitrary function to call? That is a symbolic reference, and is generally a bad idea (particularly in a CGI script - see some of Ovid's posts on that).

Instead I would suggest that you do something like this (untested): 

use Carp; # So we can get verbose error messages
# Time passes
sub ret_str_sorter {
  my $field = shift;
  my $direction = shift;
  if ('ascending' eq $direction) {
    return sub {
      $data{$a}{$field} cmp $data{$b}{$field};
    };
  }
  elsif ('descending' eq $direction) {
    return sub {
      $data{$b}{$field} cmp $data{$a}{$field};
    };
  }
  else {
    confess("Direction '$direction' not understood");
  }
}
# Time passes
my $sorter = ret_str_sorter($field, $direction);
my @ordered = sort $sorter keys %data;

[download]
ObRandomTip: Rather than working with an array of keys into a hash, instead restructure to have an array of anonymous hashes. This will generally lead to a cleaner design and no need to do things like pass the hash definition in through a global.

In reply to RE (tilly) 1: Dynamic sort algorithm selection by tilly
in thread Dynamic sort algorithm selection by Sentinel

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