go to the downloaded path and untar the tar ball and run
perl Makefile.PL prefix=$HOME
make
make install
make test
make clean
add the installed directory in $PATH variable

man warnings::unused

you will get the man page of it

but for using this module in your perl program you have to either you
-I option of perl interpreter
or 
use lib
or 
add in @INC 

it will just work fine
you can have any number of modules downloaded like this and keep in your home directory, as long as you have disk space and internet.