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

Calculating dependencies ... done!
Dependency resolution took 1.05 s (backtrack: 0/20).

[ebuild  N     ] dev-lang/mercury-22.01.1-r1::gentoo  USE="readline threads -debug -doc -emacs -examples -java -mono -profile -test -trail" 47814 KiB
[ebuild  N     ] dev-lang/mercury-extras-22.01.1::gentoo  USE="X cairo gmp ncurses opengl ssl -examples -glut -iodbc -odbc -tk -tommath -xml" 1 KiB

Total: 2 packages (2 new), Size of downloads: 47815 KiB