textproc/rfcdiff (port version rfcdiff-1.23) wants to execute
/bin/bash which is non-existing on a normal system.  (Bash installs in
/usr/local/bin.)

There are also two non-critical issues with textproc/rfcdiff:

(1) May want to add dependency to textproc/wdiff

(2) FreeBSD awk does not support --version which results in rfcdiff
printing (but otherwise working properly):

awk: unknown option --version ignored

awk: no program given

Fix: 

Patch "#!/bin/bash" to "#!/bin/sh" (or possibly patch "#!/bin/bash" to
"#!/usr/local/bin/bash" and add a runtime dependency to shells/bash)

Add a runtime dependency on textproc/wdiff

Remove the line "awkver=$($AWK --version | head -n 1)" from rfcdiff
How-To-Repeat: bengta@P142$ rfcdiff
bash: /usr/local/bin/rfcdiff: /bin/bash: bad interpreter: No such file or directory