"What is important is 16.7.0 and so on."

Are you sure about that? 16.7.0 (and darwin) refer to the Kernel Version:

[Note: I'm using Sierra 10.12.5.]

$ system_profiler SPSoftwareDataType
Software:

    System Software Overview:

      System Version: macOS 10.12.5 (16F73)
      Kernel Version: Darwin 16.6.0
      ...
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It sounds like you really want the System Version. If so, and you only want the version number, this might be easier:

$ sw_vers -productVersion
10.12.5
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To get at this information, you can use backticks, qx{}, open with '-|' mode, and other methods (the open doco has links to some of these). And, of course, add appropriate error handling.

Mac::OSVersion (already suggested by ++marto) uses both of those commands with backticks. It also provides a name() method; however, the names are hard-coded:

my @names = qw( Cheetah Puma Jaguar Panther Tiger Leopard ) ;
push @names, 'Snow Leopard', 'Lion', 'Mountain Lion',
        'Mavericks', 'Yosemite', 'El Capitan', 'Sierra',
        'High Sierra', 'Mojave';
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There's a potential problem with this. When Apple releases a new (named) version, that module will need to be updated, you'll need to upgrade to that updated version, and your users may need a similar upgrade.

If you wanted to handle the names yourself, https://support.apple.com/en-us/HT201260 has a list of names and version numbers. It looks like this information is kept up-to-date: it was last updated a month ago.