$ perl -we 'use Benchmark;
use strict;
use Fcntl;
timethese(
    5000000,
    {
        sysopen => sub {
          sysopen( my $F, "datei", O_WRONLY ) or die $!
        },
        open => sub {
          open( my $F, ">datei" ) or die $!
        }
    }
  )'
Benchmark: timing 5000000 iterations of open, sysopen...
      open: 57 wallclock secs (40.82 usr + 16.47 sys = 57.29 CPU) @ 87275.27/s (n=5000000)
   sysopen: 54 wallclock secs (39.85 usr + 13.77 sys = 53.62 CPU) @ 93248.79/s (n=5000000)