$ 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: 124 wallclock secs (53.82 usr + 62.77 sys = 116.59 CPU) @ 42885.32/s (n=5000000)
   sysopen: 84 wallclock secs (51.25 usr + 28.48 sys = 79.73 CPU) @ 62711.65/s (n=5000000)