my %filesystems = ( hosta => { desc => 'x', filesystem => [ qq|/a/b/c 
+/d/e/f| ] },
                    hostb => ( desc => 'r', filesystem => [ qq/w/e/r /
+home ] } );
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Thats how I would write the structure. Although, just a suggestion, I would use an ini file or some sort of config file to hold the host info and build %filesystems with code.

Ive used Config::INI::Reader for such things ( ini files ) and it works well.