tilly's addressed your main point, but I thought I should point out two things about get_top_sources:

1. You're never subtracting from $total when you add stuff to your return value, meaning that the "other" slice is forever too big
2. Including the "other" slice, you actually produce $max_wedges+1 wedges

Here's what I might do, but I'm a bit odd. After you calculate @sorted...:

  my @sorted = sort {
        $events{$b}{'count'} <=> $events{$a}{'count'}
               } keys %events;
  if (@sorted > $max_wedges)
  {
    map { $events{'other'}{'count'} += $_ } 
        @sorted[$max_wedges..$#sorted];
    @sorted[$max_wedges..$#sorted] = ('other');
  }
  return [map { {$_ => $events{$_}{'count'}}; } @sorted];
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Note that $total is now never used, so there's no longer any reason to be calculating it above.

This uses map heavily, which is sometimes a bit odd to get used to, but I find it leads me to write stuff that I can look at later and easily read. YMMV.