Since this module is used as a fallback in case no built-in modules

Since this module is used as a fallback in case no built-in modules
have been configured, string.atof() should not fail when "import re"
fails (usually because pcre is not there).

This opens up a tiny security hole: *if* an attacker can make "import
re" fail, they can also make string.atof(arbitrary_string) evaluate
the arbitrary string.  Nothing to keep me awake at night...