module for efficiently counting the number of lines in a file

 perlfaq5 answers the question on how to count the number of lines in a file.
 File::CountLines is a convenient wrapper around that method, with additional
 options.
 .
 More specifically, it counts the number of line breaks rather than lines. On
 Unix systems nearlly all text files end with a newline (by convention), so
 usually the number of lines and number of line breaks is equal.