Branch reset pattern

[gmarsden]

It would be nice if branch reset patterns were supported.

CL-USER> (scan-to-strings "(?|(abc)|(123))" "abcdef")
"abc"
#("abc")
CL-USER> (scan-to-strings "(?|(abc)|(123))" "123456")
"123"
#("123")

instead of the default behaviour:

CL-USER> (scan-to-strings "(abc)|(123)" "abcdef")
"abc"
#("abc" NIL)
CL-USER> (scan-to-strings "(abc)|(123)" "123456")
"123"
#(NIL "123")

See http://perldoc.perl.org/perlre.html#%28%3f|pattern%29