I like this. You don't have to.
my $mode =
(ref $hash->{CALLBACK} eq 'CODE'
? kAEQueueReply
: (exists $hash->{REPLY} # check event setting
? $hash->{REPLY}
: exists $self->{REPLY} # check global setting
? $self->{REPLY}
: 1 # default to wait
)
? kAEWaitReply
: kAENoReply)
| (exists $hash->{MODE}
? $hash->{MODE}
: exists $self->{MODE}
? $self->{MODE}
: (kAECanInteract | kAECanSwitchLayer));
