for (qw/ ,asd asd:asd asd, asd,asd asd,,asd/){
 my $test = $_;
 print "$test: ";
 print "yes" unless $test=~tr/a-zA-Z,//c or index( $test, ',') == 0 or index( $test, ',') == -1 + length( $test) or index( $test, ',,') > 0;
 print "\n";
 }