Any module you install yourself should go to site_perl, that's the meaning. Site specific modules (as opposed to core modules that come with perl). auto directories are used by the Autoloader module for segmented modules, they often contain 0-length *.bs (bootstrap) files. You get you architecture-platform module directories as well for dynamic libraries. Yours is sun4-solaris. Your home might be on a nettwork share such as mine, and linux on x86 surely couldn't use the binaries built for a sun (wheras pure perl modules can be shared and are not stored under an arch-sys dir).

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I'm not belgian but I play one on TV.