Do not write anything after the
      .include <bsd.port.mk> line.  It
      usually can be avoided by including
      bsd.port.pre.mk somewhere in the middle of
      the Makefile and
      bsd.port.post.mk at the end.
Include either the
	bsd.port.pre.mk/bsd.port.post.mk
	pair or bsd.port.mk only; do not mix
	these two usages.
bsd.port.pre.mk only defines a few
      variables, which can be used in tests in the
      Makefile,
      bsd.port.post.mk defines the rest.
Here are some important variables defined in
      bsd.port.pre.mk (this is not the complete
      list, please read bsd.port.mk for the
      complete list).
| Variable | Description | 
|---|---|
ARCH | The architecture as returned by
	      uname -m (for example,
	      i386) | 
OPSYS | The operating system type, as returned by
	      uname -s (for example,
	      FreeBSD) | 
OSREL | The release version of the operating system
	      (for example, 2.1.5 or
	      2.2.7) | 
OSVERSION | The numeric version of the operating system; the
	      same as __FreeBSD_version. | 
LOCALBASE | The base of the “local” tree (for
	      example, /usr/local) | 
PREFIX | Where the port installs itself (see
	      more on
		PREFIX). | 
When MASTERDIR is needed, always define
	it before including
	bsd.port.pre.mk.
Here are some examples of things that can be added after
      bsd.port.pre.mk:
# no need to compile lang/perl5 if perl5 is already in system
.if ${OSVERSION} > 300003
BROKEN=	perl is in system
.endifAlways use tab instead of spaces after
      BROKEN=.
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