$ ./syswrite_or_concat.pl 1000000 Double syswrite: timethis 1000000: 2 wallclock secs ( 0.43 usr + 0.94 sys = 1.37 CPU) @ 729927.01/s (n=1000000) Data concat: timethis 1000000: 1 wallclock secs ( 0.32 usr + 0.45 sys = 0.77 CPU) @ 1298701.30/s (n=1000000) Data join: timethis 1000000: 1 wallclock secs ( 0.37 usr + 0.46 sys = 0.83 CPU) @ 1204819.28/s (n=1000000)