ref

sub method {
    my ($self) = @_;
    print ref($self), "\n";
}
[download]

It's very rare to need that. Why do you ask? Maybe there's a better answer if we knew the bigger picture.

Except,

sub woot
{
   my ($self) = @_;
   print __PACKAGE__, "\n"; # <-- prints "foo"
   print ref($self), "\n";  # <-- prints nothing
}
[download]

While,

sub woot
{
   my ($self) = @_;
   print __PACKAGE__, "\n"; # <-- prints "foo"
   print $self, "\n";       # <-- prints "bar"
}
[download]

I think this is because, in this simple example, the object was never blessed. Had it been blessed, I think ikegami's answer is correct.

yeah, oops.

sub class_method {
   my ($class) = @_;
   print "$class\n";
}

sub object_method {
   my ($self) = @_;
   my $class = ref($self);
   print "$class\n";
}

Class->class_method();
$obj->object_method();
[download]

the object was never blessed.

There is no object at all. Note that the OP's call of woot is done like this:

package main;
bar->woot();
[download]

This means that he is writing a package name to the left of ->, i.e. woot is might be something like a constructor. So you don't have an object, but you do have a package name.
-- 
Ronald Fischer <ynnor@mm.st>