use Benchmark;
my $string = "1234567890" x 5000 ;

print "\$string is " . length( $string ) . " bytes \n";

timethese(-10,{split=>sub{  
					for my $c (split //, $string) {  }   
                      },
             for=>sub{ 
             
					my $c;
					for ( my $i = 0; $i < length($string); $i++ ) { 
						$c = substr( $string, $i, 1);
					}
             
              }});