Deciphering a Porter's Handbook paragraph

[Warren Block]

http://www.freebsd.org/doc/en_US.ISO8859-1/books/porters-handbook/book.html#PORTING-PREFIX

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   # make clean; make package PREFIX=/var/tmp/`make -V PORTNAME`

   If anything is installed outside of PREFIX, the package creation
   process will complain that it cannot find the files.
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Okay so far.

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   This does not test for the existence of internal references, or
   correct use of LOCALBASE for references to files from other ports.
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I want to rewrite that to be more specific about what "this" refers to:

   This simple test does not check for incorrect internal references
   or the correct use of LOCALBASE for references to files from other
   ports.

That seems a bit better.  Now for the good one:

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   Testing the installation in /var/tmp/`make -V PORTNAME` to do that
   while you have it installed would do that.
------

What?  Testing the installation... how?  Does "installation" mean 
already-installed files, or does it mean the user is supposed to do an 
installation?  What does "that" in "to do that" refer to?  What does the 
last "that" refer to?

I think it may mean:

   To test for those problems, run the program from the temporary
   installation in /var/tmp/`make -V PORTNAME` and verify that it
   operates correctly.

The complete rewritten paragraph:

   This simple test does not check for incorrect internal references
   or the correct use of LOCALBASE for references to files from other
   ports.  To test for those problems, run the program from the temporary
   installation in /var/tmp/`make -V PORTNAME` and verify that it
   operates correctly.

Please, someone help me encromulate this.