local $@;
eval {
  # ... do something ...
  return 1;
} or do {
  my $err=$@;  #prevent reset while evaluating if conditions
  if (!$err) {
    die Exception::Unknown->new();
  } elsif (!Scalar::Util::blessed($err)) {
    #ugly string regex processing here
  } elsif ($err->isa('BadParameterException')) {
    #handle bad parameters
  } elsif ($err->isa('IOException')) {
    #handle IO exceptions
  } elsif #... yada yada
  } else {
    die Exception::Unknown->new();
  }
}