>perl -wMstrict -le
"my $rx = qr/ \A [^,]* \z /x;
 ;;
 for my $s (',abcd', 'abc,d', 'abcd,', ',,,', 'abcd', '.;$%&', '') {
   print qq{'$s' }, $s =~ $rx ? '' : 'NO', ' match';
   }
"
',abcd' NO match
'abc,d' NO match
'abcd,' NO match
',,,' NO match
'abcd'  match
'.;$%&'  match
''  match