use strict;
use warnings;
use Benchmark qw/ timethese cmpthese /;

my $oBook = { SheetCount => 1000 };

cmpthese(timethese(10000, {
        'For_C'   => '&For_C',
        'For_Set' => '&For_Set',
    }));

sub For_C
{
    my $var;
    for (my $iSheet=0;
         $iSheet < $oBook->{SheetCount};
         $iSheet++)
    {
        $var = $iSheet;
    }
}

sub For_Set
{
    my $var;
    for my $iSheet (0..$oBook->{SheetCount}-1)
    {
        $var = $iSheet;
    }
}