perl5.10 dependency

[dlc]

For a portfile variant I'm am working on, I need to set a depends_lib  
for a version of perl with the usemultiplicity=yes config option which  
is perl5.10 or perl5.12.   What is  the best way to do that  
considering perl5.8 is likely already installed and one would have to  
use the +mangle_names variant.  In other words, I would need to patch  
source files if the perl port used name mangling but no patches if no  
name mangling.