Calling base constructor in perl

What is the correct way to call the base constructor from the class constructor in Perl ?

I have seen syntax like this:

 my $class = shift; 
 my $a = shift; 
 my $b = shift;
 my $self = $class->SUPER::new($a, $b);
 return $self;

Is this correct ? What if we have several parent classes. For example a class like this:

 package Gamma;
 use base Alpha;
 use base Beta;

 sub new
 {
   # Call base constructors...
 }
 1;