Sounds to me like what you want to do is sort all the entries into a hash of arrays (HoA), where the key is the prefix. Something like:

   my %sorted;
   foreach my $item (@array) {
     my ($prefix) = $item =~ /^(\w+)/;
     push @{$sorted{$prefix}}, $item;
   }
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Then you can work your way through the list of items for each prefix like this:

   foreach my $prefix (keys %sorted) {
     my @items = @{$sorted{$prefix}};
     # do something with @items...
   }
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Does that make sense?

-sam