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-libs/oniguruma-6.9.10:0/5::gentoo  USE="-crnl-as-line-terminator -static-libs" 957 KiB
[ebuild  N     ] acct-group/carbon-0-r3::gentoo  0 KiB
[ebuild  N     ] acct-user/carbon-0-r3::gentoo  0 KiB
[ebuild  N     ] app-misc/carbon-c-relay-3.9::gentoo  USE="oniguruma ssl zlib -client -lz4 -pcre2 -snappy" 465 KiB

Total: 4 packages (4 new), Size of downloads: 1421 KiB