$_ = "it's 94% fat-free!";    # a string that should match

# the following code works but the logic is outside the RE
print "match\n" if (/(\d{1,3})%/, $1>91);

# the following code also works but is offensive
print "match\n" if /(\d{1,3})%(?(?{$1>91})(?:.*)|(?!.*))/;

##</code><code>##

/(\d{1,3})%  # find a percentage to match
(?(         # begin conditional construct
?{$1>91})   # return value of a code block can be used to test
(?:.*)    # RE to use if true -- this always-true RE makes entire RE match
|
(?!.*))/  # RE to use if false -- this always-false RE makes entire RE fail