Also, if you are trying to grab lines based on the number of fields, you could do:

do_something_with($line) if (@{[split / /, $line]} == 3);

... to grab all of the lines that have 3 fields in them.

The following is a little faster, but throws a warning:

do_something_with($line) if ((scalar split / /, $line) == 3);

Of course, if you are looking at more than the number of fields, these won't be useful ...
--jrtayloriv