That's because $ct refers to the value of the entire Contact header, not
just the URI portion.
You need to get at the URI portion first:
xlog("L_INFO", "$(ct{nameaddr.uri}{uri.user})\n");
--
Alex Balashov - Principal
Evariste Systems LLC
235 E Ponce de Leon Ave
Suite 106
Decatur, GA 30030
United States
Tel: +1-678-954-0670
Web:
http://www.evaristesys.com/,
http://www.alexbalashov.com/