if ($subkey == 1) {
            $acc = $messagebin{$file}{$subkey};
            if($debug){&writelog(3,"DEBUG: Account=$acc");}
         } elsif ($subkey == 11) {
            $ordid = $messagebin{$file}{$subkey};
            if($debug){&writelog(3,"DEBUG: OrderId=$ordid");
         } elsif ($subkey == 14) {
            ...
         } else { # you should _always_ have an else branch
           warn "Unhandled subkey value $subkey.";
         };

##</code><code>##

my $acc;
my %handler = (
  1  => sub { $acc = $messagebin{$file}{1}; },
  11 => sub { ... },
);

if (my $code = $handler{+$subkey}) {
  $code->($subkey);
  # I found it convenient to have the dispatch value
  # available in the dispatch handler
} else {
  warn "Unhandled subkey value $subkey";
};