clarify dynamic prereqs in docs

diff --git a/Changes b/Changes
index 8dc11db..93d872c 100644 (file)
--- a/Changes
+++ b/Changes
@@ -1,5 +1,8 @@
 Revision history for JSON-MaybeXS
 
+ - added an INSTALLATION section to documentation, to clarify the use of
+   dynamic prerequisites in Makefile.PL
+
 1.003007 - 2016-09-11
  - no changes since 1.003006_001
 

diff --git a/lib/JSON/MaybeXS.pm b/lib/JSON/MaybeXS.pm
index 14d2d00..457a955 100644 (file)
--- a/lib/JSON/MaybeXS.pm
+++ b/lib/JSON/MaybeXS.pm
@@ -274,6 +274,23 @@ Alternatively, you can use duck typing:
     use Moose::Util::TypeConstraints 'duck_type';
     is 'json' => ( isa => Object , duck_type([qw/ encode decode /]));
 
+=head1 INSTALLATION
+
+At installation time, F<Makefile.PL> will attempt to determine if you have a
+working compiler available, and therefore whether you are able to run XS code.
+If so, L<Cpanel::JSON::XS> will be added to the prerequisite list, unless
+L<JSON::XS> is already installed at a high enough version. L<JSON::XS> may
+also be upgraded to fix any incompatibility issues.
+
+Because running XS code is not mandatory and L<JSON::PP> (which is in perl
+core) is used as a fallback backend, this module is safe to be used in a suite
+of code that is fatpacked or installed into a restricted-resource environment.
+
+You can also prevent any XS dependencies from being installed by setting
+C<PUREPERL_ONLY=1> in F<Makefile.PL> options (or in the C<PERL_MM_OPT>
+environment variable), or using the C<--pp> or C<--pureperl> flags with the
+L<cpanminus client|cpanm>.
+
 =head1 AUTHOR
 
 mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>