[cl-ppcre-devel] differing results between cl-ppcre and perl -- operator precedence?

[Cyrus Harmon]

In trying to track down a problem matching a cxml-rng pattern in soiree, I came across the following somewhat odd behavior in cl-pppcre.

In perl, I see:

(sly at barbaresco):~/projects/soiree$ echo "Ta" | perl -ne 'print if /^T(a)|(b)$/'
Ta

(sly at barbaresco):~/projects/soiree$ echo "Tb" | perl -ne 'print if /^T(a)|(b)$/'
Tb

Whereas with cl-ppcre, I see:

SOIREE-ICALENDAR> (cl-ppcre:scan-to-strings "^T(a)|(b)$" "Ta")
"Ta"
#("a" NIL)

SOIREE-ICALENDAR> (cl-ppcre:scan-to-strings "^T(a)|(b)$" "Tb")
"b"
#(NIL "b")

Parsing the string suggests that the order of operations may be different in cl-ppcre than in perl. Is this intentional?

SOIREE-ICALENDAR> (cl-ppcre:parse-string "^T(a)|(b)$")
(:ALTERNATION (:SEQUENCE :START-ANCHOR #\T (:REGISTER #\a))
 (:SEQUENCE (:REGISTER #\b) :END-ANCHOR))

thanks,

Cyrus