C:\Daten\perl>benchmark.pl
Benchmark: timing 100 iterations of A, A2, C, D...
         A: 307 wallclock secs (272.94 usr + 27.55 sys = 300.49 CPU) @  0.33/s (n=100)
        A2: 316 wallclock secs (278.64 usr + 24.92 sys = 303.56 CPU) @  0.33/s (n=100)
         C: 333 wallclock secs (278.80 usr + 23.83 sys = 302.63 CPU) @  0.33/s (n=100)
         D:  0 wallclock secs ( 0.00 usr +  0.00 sys =  0.00 CPU)
            (warning: too few iterations for a reliable count)

#!/usr/bin/perl
use strict;
use warnings;
use Benchmark;

my $file = 'test.txt';

timethese(100, {
    A  => sub {
               open ( FILE, $file );
               my $ln;
               $ln++ while <FILE>;
               close (FILE);
              },

    A2 => sub {
               my $ln;
               open ( FILE, $file );
               ++$ln while <FILE>;
               close (FILE);
              },
    # ist unter C ein Unterschied, spart temporäre Variable...

    #B  => sub {
    #           open ( FILE, $file );
    #           my @array;
    #           my $ln = scalar(@array = <FILE>);
    #           close (FILE);
    #          },

    C  => sub {
               open ( FILE, $file );
               while ( <FILE> ) {}
               my $ln = $.;
               close (FILE);
              },

    D  => sub {
               my $ln = -s $file;
              },
              }
          );

# test.txt hat 3.804.144 Zeilen und ist 195.338.421 Byte groß