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copied!<p>I don't think buffering has much to do with it. I'm guessing it's because the terminal needs to scroll when you print a newline to it (or print enough characters to fill a line). When I benchmark these functions writing to a file or to <code>/dev/null</code>, there is not much of a difference. </p> <pre><code>use Benchmark; timethis(1000000, 'main'); timethis(1000000, 'main2'); select STDERR; $| = 0; select STDOUT; # enable buffering on STDERR sub main { print STDERR "you are the bomb. \n" } sub main2 { print STDERR "you are the bomb. " } $ perl benchmark.pl 2> a_file timethis 1000000: 21 wallclock secs ( 4.67 usr + 13.38 sys = 18.05 CPU) @ 55410.87/s timethis 1000000: 21 wallclock secs ( 4.91 usr + 13.34 sys = 18.25 CPU) @ 54797.52/s $ perl benchmark.pl 2> /dev/null timethis 1000000: 26 wallclock secs ( 2.86 usr + 10.36 sys = 13.22 CPU) @ 75648.69/s timethis 1000000: 27 wallclock secs ( 2.86 usr + 10.30 sys = 13.16 CPU) @ 76010.95/s $ perl benchmark.pl 2> a_file (without buffering) timethis 1000000: 29 wallclock secs ( 3.78 usr + 12.14 sys = 15.92 CPU) @ 62806.18/s timethis 1000000: 29 wallclock secs ( 3.27 usr + 12.51 sys = 15.78 CPU) @ 63367.34/s $ perl benchmark.pl 2> /dev/tty (window has 35 lines and buffers 10000, YMMV) [ 200000 declarations of how you are a bomb deleted ] timethis 100000: 53 wallclock secs ( 0.98 usr + 3.73 sys = 4.72 CPU) @ 21190.93/s timethis 100000: 9 wallclock secs ( 0.36 usr + 1.94 sys = 2.30 CPU) @ 43535.05/s </code></pre> <p>Summary: extra flushing reduces performance by about 10%. Extra scrolling on the terminal reduces performance by about 50%.</p>

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