Look it is very case sensitive...
/(?<token>[0-9]+)/* - link /index/123456 - :VAR(token);
/(?<token>[a-z]+[0-9]+)/* - link /index/abcdtoz0123456789 - :VAR(token);
/(?<token>[A-Z]+[a-z]+[0-9]+)/* - link /index/ABCabc01239 - :VAR(token);
/(?<token>[a-z-0-9]+)/* - link /index/a1b2c3d4 - :VAR(token);
if multiple then url must be sensitive
/(?<token>[a-z]+)/*/(?<session>[0-9]+)/* - link /index/abcd/012349 - token is: :VAR(token); and session: :VAR(session);
if tripple then url also must be sensitive
/(?<token>[a-z]+)/*/(?<session>[A-Z]+)/*/(?<apikey>[0-9]+)/* - link /index/abcd/ABCDE/012349
if want to reject some number
/(?<token>[0-5]+)/* - link /index/0123456789 - :VAR(token); 6789 will not show
if want start Capital
/(?<token>[A-z]+)/* - link /index/Wapka /index/wapka
