As it happens, merlyn posted something similar the other day, which you could adapt easily (untested)...

# in Astro::Observation

sub new {
    my $self  = shift;

    # Foo->new('bar',@_) => Foo::Bar->new(@_)

    my $class = __PACKAGE__ . "::" . ucfirst(shift);

    require autouse;
    autouse->import( $class, "$class\::new" );

    return $class->new( @_ );
}
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Update:

... or not.

After trying out the above, I kept getting the error "autouse into different package attempted", which appears to be a known bug in autouse when using a module that isn't at the root of it's namespace (ie, Foo would work, but Foo::Bar doesn't).

Perhaps merlyn has a patched version of autouse?

Anyhoo, another way to do it (and as jeffa suggests) is with eval...

sub new {
    my $self  = shift;

    # Foo->new('bar',@_) => Foo::Bar->new(@_)

    my $class = __PACKAGE__ . "::" . ucfirst(shift);

    eval "require $class;"; # Note: "" *NOT* {} !

    if ( $@ ) {      # whoops, there was an error
        warn( $@ );  # require'ing $class; perhaps
        return;      # it doesn't exist?
    }

    return $class->new( @_ );
}
[download]

    --k.