The following works fine:

====
%(kernel_v < "2.6.40" %?
probe end {}
%)
====

However, the following fails:

====
%(kernel_v < "2.6.40" %?
probe ioblock.* {}
%)
====

# stap -vp4 ../preprocessor.stp 
parse error: expected identifier or '*'
	saw: operator '*' at ../preprocessor.stp:2:15
     source: probe ioblock.* {}
                           ^
1 parse error(s).
Pass 1: parsed user script and 70 library script(s) using
33604virt/20496res/1604shr kb, in 170usr/20sys/202real ms.
Pass 1: parse failed.  Try again with another '--vp 1' option.

(If nothing else, the error message is very confusing, since it complains it
found a '*' while looking for a '*'.)