Hi,

I would like to define a regular expression that matches strings consisting of two sub-strings separated by a single comma. Each sub-string may not be empty, and consists exclusively and without repetition of the characters 'A', 'G', 'C' and 'T'. Thus, the pattern should match strings such as:

A,G
AG,CT
TC,CA <- correct, 1st and 2nd sub-strings may have characters in common
( as long as these are not repeated within the sub-string ).
GAT,CGA
CGAT,TG <- correct, sub-strings may be of different length.
etc ...

and should not match:

,G <- missing 1st sub-string
ACGT <- missing comma
X,A <- incorrect character X
AA,G <- repetition of character A in 1st substring
AC,GGC <- repetition of character G in 2nd sub-string
ATGA,TGG <- repetition in both sub-strings
ATCXG,AAC <- incorrect character X and repetition in 2nd
sub-string
etc ...

So far I have:

/^(?=[ACGT]{1,4},[ACGT]{1,4}$)(?!.*(.).*\1.*,)(?!,.*(.).*\1).*$/

/^(?=[ACGT]{1,4},[ACGT]{1,4}$)(?!.*(.).*\g{1}.*,)(?!,.*(.).*\g{1}).*$/

also tried joining the capture groups with:

Now, (?=[ACGT]{1,4},[ACGT]{1,4}$) seems to match the "two sub-strings separated by a single comma" and "consists exclusively of the characters 'A', 'G', 'C' and 'T'" through out the string;

(?!.*(.).*\1.*,)seems to match "without repetition" up to the comma.

However, (?!,.*(.).*\1)appears not to be ensuring that it doesn't match a repeated character after the comma.

I'd greatly appreciate replies with clues and/or patterns that help with the desired matching.

Using perl v5.18.2

Thanks in advance

Robert