cmpthese 1, {
    a=>q[ qx[ touch         junka.$_  ] for 1 .. 1000 ],
    b=>q[ do{ open my $f, ">junkb.$_" } for 1 .. 1000 ],
};;

  s/iter     a     b
a   8.83    --  -95%
b  0.421 1997%    --