Tcl regex Vs. Java regex (Cloverleaf GUI)

I have had some that have used the grepDB script ask about why a regexp that works in Tcl does not work in the SMAT DB GUI so, even though it is documented, (who reads docs)  😀  I thought I would post this.

Copied from my script comments so 80 byte lines.

A note about using regular expressions in Tcl vs using regular expressions

in the SMAT DB GUI (Java)

The Cloverleaf documentation states that Java, by default, does not treat

CR or NL as regular characters so a dot (.) would not recognize a CR or NL

and you must use the expression (?s) to cause the Java regexp engine

to treat CR NL as regular characters so you can search across segments.

Tcl regexp is just the opposite.  By default, CR and NL are treated as

just regular charaters so a search like ORU.*OBR would work OK in Tcl

while in Java (CL GUI) it would be like (?s)ORU.*OBR.  To emulate the

Java behavior in Tcl use (?n) whch is equivalent to the -line option

when using the Tcl regex command.

Be aware of this when trying to use regular expressions in any

Tcl procedure then use the same in the CL SMAT DB GUI or vice versa!