BEGIN{ FS="\t"; OFS="\t"; }
{
 	possible_labels=$1;
 	rowid=$2;
    label=$3;
    features=$4;

 	label_count = split(possible_labels, label_array, ",");
 		
	for(i = 1; i <= label_count; i++) {
    	if (label_array[i] == label)
      		print rowid, label, 1, features;
      	else
      		print rowid, label_array[i], -1, features;
	}
}
END{}

Add an awk script used in one-vs-the-rest classification example.