c:\@Work\Perl\monks>perl -wMstrict -le
"use Data::Dump qw(pp);
 ;;
 for my $str ('0,1,.5,0,1',  '.5,,0,1,',  ',,,,',  '123', '',) {
   ;;
   my @ra =  split ( ',' , $str, -1 );
   my $spstr = join ',', @ra;
   printf qq{'$str' -> %s -> >$spstr< \n}, pp(\@ra);
   die qq{split/join not orthogonal: '$str' '$spstr'} unless $str eq $spstr;
   }
"
'0,1,.5,0,1' -> [0, 1, ".5", 0, 1] -> >0,1,.5,0,1<
'.5,,0,1,' -> [".5", "", 0, 1, ""] -> >.5,,0,1,<
',,,,' -> ["", "", "", "", ""] -> >,,,,<
'123' -> [123] -> >123<
'' -> [] -> ><