package SomeClass;
#...
sub some_method {
  # ...
  eval { die("Oops!"); };
  if($@) {
    $self->{'errstr'} = "Something has gone wrong: $@";
    return(undef)
  }
  # ...
}
#...
package main;
#...
my $result = $obj->some_method;
unless(defined($result)) {
  die("Can't SomeClass->some_method(): $obj->{'errstr'}");
}
#...