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/Future-0.520.0::gentoo  USE="-test" PERL_FEATURES="ithreads (-debug) -quadmath" 104 KiB
[ebuild  N     ] dev-perl/Struct-Dumb-0.160.0::gentoo  USE="-test" PERL_FEATURES="ithreads (-debug) -quadmath" 22 KiB
[ebuild  N     ] dev-perl/IO-Async-0.804.0::gentoo  USE="-test" PERL_FEATURES="ithreads (-debug) -quadmath" 249 KiB

Total: 3 packages (3 new), Size of downloads: 373 KiB