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

Calculating dependencies ... done!
Dependency resolution took 2.56 s (backtrack: 3/20).

[ebuild  N     ] dev-libs/libaio-0.3.113_p8::gentoo  USE="-static-libs -test" 74 KiB
[ebuild  N     ] dev-debug/strace-7.2::gentoo  USE="aio ncurses -elfutils -perl (-selinux) -static -test -unwind -verify-sig" 2745 KiB
[ebuild  N     ] dev-lisp/asdf-3.3.5-r1:0/3.3.5-r1::gentoo  USE="-doc -test" 509 KiB
[ebuild  N     ] dev-lisp/uiop-3.3.5::gentoo  102 KiB
[ebuild  N     ] dev-lisp/sbcl-2.6.9:0/2.6.9::gentoo  USE="threads unicode zstd -debug -doc -source -system-bootstrap" 21241 KiB
[ebuild  N     ] virtual/commonlisp-0-r1::gentoo  0 KiB
[ebuild  N     ] dev-lisp/trivial-gray-streams-20170830-r1::gentoo  8 KiB
[ebuild  N     ] dev-lisp/flexi-streams-1.0.19::gentoo  USE="-test" 385 KiB
[ebuild  N     ] dev-lisp/cl-ppcre-2.1.0-r1::gentoo  156 KiB
[ebuild  N     ] dev-lisp/cl-unicode-0.1.5-r1::gentoo  475 KiB
[ebuild  N     ] dev-lisp/cl-ppcre-unicode-2.1.0-r1::gentoo  0 KiB

Total: 11 packages (11 new), Size of downloads: 25691 KiB

WARNING: One or more updates/rebuilds have been skipped due to a dependency conflict:

dev-lisp/cl-ppcre:0

  (dev-lisp/cl-ppcre-2.1.2:0/0::gentoo, ebuild scheduled for merge) USE="" conflicts with
    =dev-lisp/cl-ppcre-2.1.0-r1


!!! The following update(s) have been skipped due to unsatisfied dependencies
!!! triggered by backtracking:

dev-lisp/cl-ppcre-unicode:0