Debian release of PCRE 4.5 had PCRE_LIB_VERSION=13:0:10 PCRE_POSIXLIB_VERSION=13:0:10 which corresponds to latest debian-revision (soname libpcre.so.3, installed as libpcre.so.3.9.0) and followed the instructions about version numbering in the libtool manual: | 3. If the library source code has changed at all since the last | update, then increment REVISION (`C:R:A' becomes `C:r+1:A'). 13:1:10 4. If any interfaces have been added, removed, or changed since the last update, increment CURRENT, and set REVISION to 0. 14:0:10 5. If any interfaces have been added since the last public release, then increment AGE. 14:0:11 6. If any interfaces have been removed since the last public release, then set AGE to 0. n/a Therefore I'm using 14:0:11 for this release of PCRE 5.0