Scorer cannot handle VCF files with comma-separated list in ALT field (column 5)

According to the VCF format specification (v4.0):

ALT comma separated list of alternate non-reference alleles called on at least one of the samples. Options are base Strings made up of the bases A,C,G,T,N, or an angle-bracketed ID String (”<ID>”). If there are no alternative alleles, then the missing value should be used. Bases should be in uppercase. (Alphanumeric String; no whitespace, commas, or angle-brackets are permitted in the ID String itself)