How to install JavaScript::SpiderMonkey

Get the latest SpiderMonkey distribution from mozilla.org:
http://www.mozilla.org/js/spidermonkey shows which releases are available.
http://ftp.mozilla.org/pub/js/js-1.5-rc3a.tar.gz has been proven to work.

Untar it at the same directory level as the distribution of the
JavaScript::SpiderMonkey perl module distribution whichs README
you're currently reading:

cd ..
tar zxfv js-1.5-rc3a.tar.gz

It's important that the js and JavaScript-SpiderMonkey-v.vv directories
are at the same level:

$ls
JavaScript-SpiderMonkey-1.00  
js
js-1.5-rc3a.tar.gz

Alternatively, specify the location of the library on the command line
to Makefile.PL using the --js_lib_dir and --js_lib_name options:

perl Makefile.PL --js_lib_dir /path/to/library/ --js_lib_name js

Next, build JavaScript::SpiderMonkey in the standard way:

cd JavaScript-SpiderMonkey-1.00
perl Makefile.PL
gmake
gmake test
gmake install