I like using the template method for factory operations (i.e., bless a new object that is not necessiarily part of the class you are doing this from). This allows you to avoid hard-coding the class you bless into. Example (admittedly arbitrary):

package Foo;
sub FACTORY_CLASS () { 'Bar' }

sub make_new_bar 
{
    my $self = shift;
    my @params = @_;
    bless \@params, $self->FACTORY_CLASS();
}
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This allows a subclass to easily change the class of the object without having the override the entire factory method, which could be quite complex and would lead to a lot of code duplication.

It's important that FACTORY_CLASS is called in $obj->method() form, and not plain method() form. Otherwise, subclasses won't be able to override it, which is the whole point.