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

Calculating dependencies ... done!
Dependency resolution took 1.00 s (backtrack: 0/20).

[ebuild  N     ] dev-perl/prefork-1.50.0::gentoo  USE="-test" PERL_FEATURES="ithreads (-debug) -quadmath" 28 KiB
[ebuild  N     ] dev-perl/Number-WithError-1.10.0-r1::gentoo  USE="-test" PERL_FEATURES="ithreads (-debug) -quadmath" 39 KiB

Total: 2 packages (2 new), Size of downloads: 66 KiB