8.2.1 Problem
You need to compute the number of lines in a file.

8.2.2 Solution
Many systems have a wc program to count lines in a file:

$count = `wc -l < $file`;
die "wc failed: $?" if $?;
chomp($count);
You could also open the file and read line-by-line until the end, counting lines as you go:

open(FILE, "<", $file) or die "can't open $file: $!";
$count++ while <FILE>;
# $count now holds the number of lines read
Here's the fastest solution, assuming your line terminator really is "\n":

$count += tr/\n/\n/ while sysread(FILE, $_, 2 ** 20);