$ ocaml -version
The OCaml toplevel, version 4.02.1
$ opam --version
1.2.0
$ opam init
$ opam install core
#=== ERROR while installing camlp4.4.02.1+system ==============================#
# opam-version 1.2.0
# os linux
# command sh ./check-camlp4.sh
# path /home/john/.opam/system/build/camlp4.4.02.1+system
# compiler system (4.02.1)
# exit-code 1
# env-file /home/john/.opam/system/build/camlp4.4.02.1+system/camlp4-32324-f0f09f.env
# stdout-file /home/john/.opam/system/build/camlp4.4.02.1+system/camlp4-32324-f0f09f.out
# stderr-file /home/john/.opam/system/build/camlp4.4.02.1+system/camlp4-32324-f0f09f.err
### stdout ###
# ...[truncated]
# 4.02 by switching to a local installation via `opam switch 4.02.1`.
#
# Here are some installation instructions for camlp4 …
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