+ gzip => { use => 1, extension => 'gz', flags => compressor('gzip -9', sub { $ENV{GZIP} = '-9'; '--gzip' }) },
+ bzip2 => { use => 1, extension => 'bz2', flags => compressor('bzip2 -9', sub { $ENV{BZIP2} = '-9'; '--bzip2' }) },
+ xz => { use => 1, extension => 'xz', flags => compressor('xz -9', sub { $ENV{XZ_OPT} = '-9'; '--xz' }) },
+ lzip => { use => 0, extension => 'lz', flags => compressor('lzip -9', '--lzip') },