my $subpackage = __PACKAGE__ . '::Command';
my $test_command = $subpackage->new(@ARGV);

##</code><code>##

sub UNIVERSAL::subpackage { join '::', @_ }

package Foo::Command;

sub wow { print "I am: ", __PACKAGE__, "\n" }

package Foo;

sub check { __PACKAGE__->subpackage( 'Command' )->wow() }

package main;

Foo->check();
__END__
I am: Foo::Command