Tcl Regular Expression Match Requirements describes a set of regular expressions, and what, ideally, they would match.
Tcl's regular expression engine has a particular design that leads to some unexpected results. The collection below of regular expression applications on this page and their ideal results is intended as a guide for the further development of regular expression routines in Tcl.
Ideal:
% regexp -inline -indices {(t*?)?} ttt
{0 -1} {0 -1}Actual:
% regexp -inline -indices {(t*?)?} ttt
{0 2} {0 2}Ideal and actual:
regexp -indices -inline {.*(a*){1,3}?} aaaa
{0 3} {4 3}If there is a quantifier on a capturing expression, it should return a list of matches:
% regexp -indices -inline {(a.*?f)*} aaafaaafjkl
{0 7} {{0 3} {4 7}}Actual:
% regexp -indices -inline {(a.*?f)*} aaafaaafjkl
{0 7} {4 7}