Example how to cache for perl `cpm`

[KES777]

FROM perl

RUN  cpanm -n -L ./local App::cpm Carton::Snapshot  && rm -rf /root/.cpanm
COPY cpanfile ./
COPY cpanfile.snapshot ./

RUN  --mount=type=cache,id=perl,target=/root/.perl-cpm   \
  cpm install  -w 16  --no-test  -L ./local