The app_dir statement is deprecated. As far as I can tell no one is using it.
app_dir
If you do use it, it will only affect initial generation with -c. Then it specifies the name of the build directory. Normally the name of the build directory is taken from the app name as h2xs does it.
Note that only a single path element is allowed. You cannot specify depth as in 'under/here'. For that you need the equally deprecated base_dir.
base_dir
To see an example, build:
bigtop -c example.bigtop all
Note that the build directory is called useless_dir instead of Kids.
useless_dir
Kids
To install Bigtop, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Bigtop
CPAN shell
perl -MCPAN -e shell install Bigtop
For more information on module installation, please visit the detailed CPAN module installation guide.