gistfile1.py

def invalid_cusip(cusip):
    """

    :param cusip:
    :type cusip: str
    :return:
    """
    cusip = cusip.upper()
    if len(cusip) > 9:
        return 'CUSIP is too long'

    if re.search(r'[^A-Z0-9*@#]', cusip):
        return 'CUSIP contains invalid characters'

    cusip = cusip.zfill(9)
    if not cusip[8].isdigit():
        return 'CUSIP check digit out of range'

    total = 0
    for i in range(0, 7):
        value = None
        char = cusip[i]
        if char.isdigit():
            value = int(char)
        elif char.isalpha():
            value = ord(char) - ord('A') + 10
        elif char == '*':
            value = 36
        elif char == '@':
            value = 37
        elif char == '#':
            value = 38

        if i % 2:
            value *= 2

        total += int(value / 10) + value % 10

    if (10 - (total % 10)) % 10 == int(cusip[8]):
        return False
    else:
        return 'CUSIP has bad check digit'

gistfile2.pl

sub invalid_cusip {
    my ( $cusip ) = @_;

    $cusip = uc( $cusip );

    if ( length( $cusip ) > 9 ) {
        return 'CUSIP is too long';
    }

    if ( $cusip =~ /[^A-Z0-9*@#]/ ) {
        return 'CUSIP contains invalid characters';
    }

    $cusip = sprintf( "%09s", $cusip );
    my @chars = split( //, $cusip );
    if ( $chars[8] !~ /\d/ ) {
        return 'CUSIP check digit out of range';
    }
    my $total = 0;
    for ( 0 .. 7 ) {
        my $value;
        my $char = $chars[$_];
        if ( $char =~ /\d/ ) {
            $value = $char;
        } elsif ( $char =~ /[A-Z]/ ) {
            $value = ord($char) - ord('A') + 10;
        } elsif ( $char eq '*' ) {
            $value = 36;
        } elsif ( $char eq '@' ) {
            $value = 37;
        } elsif ( $char eq '#' ) {
            $value = 38;
        } else {
            die "This can't happen";
        }
        $value *= 2 if $_ % 2;
        $total += int( $value / 10 ) + $value % 10;
    }
    
    return ( $total % 10 + $chars[8] ) % 10 ? 'CUSIP has bad check digit' : 0;
}