The
PF User's Guide has an example of the
match filter used with scrub. Note, please, that the PF User's Guide is only for the most recent release, which at this time is OpenBSD 5.2. (OpenBSD 5.3 is expected to be released on or about 1 May.)
The options for scrub can be found in the
PACKET NORMALIZATION section of the pf.conf(5) man page, which has a second example of the
match filter used with scrub and a different set of normalization options. A third example may be found in the
EXAMPLES section of the man page. Lastly, the definitive syntax for scrub may be found in the
GRAMMAR section of the man page.