where to start with OPAM errors

[Heidi Howard <hh360@xxxxxxxxx>]

another day, another question :)

$opam install exited erroneously with the following error. I have no
idea really were to start to try to identify the issue, any
suggestions ?

Due to some errors while processing pcre-ocaml.7.0.2, the following
actions will NOT be proceeded:
 - install core_extended.109.21.00

==== ERROR [while installing pcre-ocaml.7.0.2] ====
# opam-version    1.0.0
# os              linux
# command         make
# path            /auto/homes/hh360/.opam/4.00.1/build/pcre-ocaml.7.0.2
# exit-code       2
# env-file
/auto/homes/hh360/.opam/4.00.1/build/pcre-ocaml.7.0.2/pcre-ocaml-865888.env
# stdout-file
/auto/homes/hh360/.opam/4.00.1/build/pcre-ocaml.7.0.2/pcre-ocaml-865888.out
# stderr-file
/auto/homes/hh360/.opam/4.00.1/build/pcre-ocaml.7.0.2/pcre-ocaml-865888.err
### stdout ###
...[truncated]
with_pcre_config: .................................... pcre-config
Strict compile-time checks: .......................... true
Build examples: ...................................... true
Create documentations: ............................... true
Compile tests executable and library and run them: ... false
ocamldoc: ............................................
/auto/homes/hh360/.opam/4.00.1/bin/ocamldoc

ocaml setup.ml -build
/auto/homes/hh360/.opam/4.00.1/bin/ocamlopt.opt -I
/auto/homes/hh360/.opam/4.00.1/lib/ocaml/ocamlbuild unix.cmxa
/auto/homes/hh360/.opam/4.00.1/lib/ocaml/ocamlbuild/ocamlbuildlib.cmxa
myocamlbuild.ml
/auto/homes/hh360/.opam/4.00.1/lib/ocaml/ocamlbuild/ocamlbuild.cmx -o
myocamlbuild
Exception End_of_file.
### stderr ###
/bin/sh: 1: pcre-config: not found
E: Failure("Command ''/auto/homes/hh360/.opam/4.00.1/bin/ocamlbuild'
lib/libpcre_stubs.a lib/dllpcre_stubs.so lib/pcre.cma lib/pcre.cmxa
lib/pcre.a lib/pcre.cmxs examples/cloc/cloc.native
examples/count_hash/count_hash.native
examples/pcregrep/pcregrep.native examples/subst/subst.native -tag
debug' terminated with error code 100")
make: *** [build] Error 1

Thank you so much for your help :)
--
Regards
Heidi