to trigger/signal a rebuild for the transition 5.8.8 -> 5.10.0.
The list of packages is computed by finding all packages which end
up having either of PERL5_USE_PACKLIST, BUILDLINK_API_DEPENDS.perl,
or PERL5_PACKLIST defined in their make setup (tested via
"make show-vars VARNAMES=...").
slurp takes:
* a filename,
* a filehandle,
* a typeglob reference,
* an IO::File object, or
* a scalar reference,
converts it to an input stream if necessary, and reads in the entire
stream. If slurp fails to set up or read the stream, it throws an
exception.
