These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 0.98 s (backtrack: 0/20).

[ebuild  N     ] dev-perl/common-sense-3.750.0::gentoo  PERL_FEATURES="ithreads (-debug) -quadmath" 14 KiB
[ebuild  N     ] dev-perl/Canary-Stability-2013.0.0::gentoo  PERL_FEATURES="ithreads (-debug) -quadmath" 5 KiB
[ebuild  N     ] dev-perl/IO-AIO-4.810.0::gentoo  USE="-test" PERL_FEATURES="ithreads (-debug) -quadmath" 186 KiB

Total: 3 packages (3 new), Size of downloads: 204 KiB