The following snippet won't actually figure out what the circular dependency is, but it will report if that is the problem, and will at least cut down the list to just the circular dependencies and things that depend on the circular dependencies. It shouldn't be too hard for you to modify this to find an actual recursive dependency in your list.

use Data::Dumper;
$Data::Dumper::Indent = 1;

my @remove;
while (%depend) {
  # Clear dependencies
  foreach my $dep (values %depend) {
    @$dep = grep {exists $depend{$_}} @$dep;
  }

  # What can I remove?
  my @can_remove = grep {0 == @{$depend{$_}}} keys %depend; 
  if (@can_remove) {
    delete $depend{$_} foreach @can_remove;
    push @remove, @can_remove;
  }
  else {
    # Uh, oh
    print "CIRCULAR DEPENDENCIES DETECTED\n";
    print Data::Dumper->Dump ([\%depend], ['*depend']);
    die "ABORTING";
  }
}
print Data::Dumper->Dump([\@remove], ['*remove']);
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