The Text.Regex.PCRE module provides a backend for regular expressions. If you import this along with other backends, then you should do so with qualified imports, perhaps renamed for convenience.
You will need to have libpcre, from www.pcre.org, to use this module. The haskell must be compiled with -DHAVE_PCRE_H and linked with pcre. This is the default in the cabal file.
If you do not compile with 1 then the functions will still
exist, but using them will create a run time error. You can test for
the existance of PCRE by checking
getVersion which is
not compiled with PCRE or
String if PCRE is present.
The regular expression can be provided as a
ByteString, but it will
be copied and a NUL byte appended to make a
CString unless such a
byte is already present. Thus the regular expression cannot contain
an explicit NUL byte. The search string is passed as a
and may contain NUL bytes and does not need to end in a NUL
ByteStrings are searched in place (via unsafeUseAsCStringLen).
String will be converted into a
processing. Doing this repeatedly will be very inefficient.
The Text.Regex.PCRE.String, Text.Regex.PCRE.ByteString, and Text.Regex.PCRE.Wrap modules provides both the high level interface exported by this module and medium- and low-level interfaces that returns error using Either structures.