It's tough to handle backwards compatibility breaks sanely in a dynamic environment. I agree that if you want to avoid disruption entirely in Perl 5, package renaming is the only option, and have in fact done something like what you recommend in the past.

Things would be easier if the language offered namespace aliasing a la Python and the community had a tradition of Java-like package namespaces.

use org::apache::spamassassin3::Mail::SpamAssassin as SpamAssassin;
my $spamtest = SpamAssassin->new();
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Using the aliased module, you can almost get there in Perl 5, though aliased only aliases one package at a time rather than the whole hierarchy.

# Works:

use aliased 'org::apache::spamassassin3::Mail::SpamAssassin';
my $spamtest = SpamAssassin->new();

# Doesn't work:

use aliased org::apache::spamassassin3 => 'SA';
my $spamtest = SA::Mail::SpamAssassin->new();
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Can you imagine the abuse that would rain down on someone who uploaded a tarball like org::apache::spamassassin3-3.31.tar.gz to CPAN, though?