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

Calculating dependencies ... done!
Dependency resolution took 1.01 s (backtrack: 0/20).

[ebuild  N     ] dev-cpp/magic_enum-0.9.8::gentoo  USE="-examples -test" 202 KiB
[ebuild  N     ] sci-libs/libsemigroups-3.5.5:0/3::gentoo  USE="(-eigen) -test" CPU_FLAGS_X86="popcnt" 13498 KiB

Total: 2 packages (2 new), Size of downloads: 13700 KiB