def sequence_compare_v1(seq1, seq2):
    """Compare sequences seq1 and seq2 and report all positions in which
       they fail to match."""
    # Determine the length of each sequence
    len1 = len(seq1)
    len2 = len(seq2)
    # Prepare our list of mismatches
    mismatches = []
    # Step through the sequences, checking for mismatches
    for pos in range(0, min(len1, len2)):
        if seq1[pos] != seq2[pos]:
            mismatches.append(pos)
    return mismatches