P:\test>perl -MBenchmark=cmpthese -le" cmpthese( -1, {    
    glob=>q[
        @f=@d=();
        push @{ -d() ? \@d : \@f }, $_ for glob('*');
    ], 
    readdir=>q[ 
        @d=@f=();
        opendir D, '.'; 
        push @{ -d() ? \@d : \@f }, $_ while $_ = readdir D;
    ] 
});"

          Rate    glob readdir
glob    22.9/s      --    -48%
readdir 44.4/s     94%      --