pcre_study()</b>
  <i>match_limit</i>  Limit on internal resource use
  <i>match_limit_recursion</i>  Limit on internal recursion depth
  <i>callout_data</i> Opaque data passed back to callouts
  <i>tables</i>       Points to character tables or is NULL
</pre>
The flag bits are PCRE_EXTRA_STUDY_DATA, PCRE_EXTRA_MATCH_LIMIT,
PCRE_EXTRA_MATCH_LIMIT_RECURSION, PCRE_EXTRA_CALLOUT_DATA, and
PCRE_EXTRA_TABLES. For this matching function, the <i>match_limit</i> and
<i>match_limit_recursion</i> fields are not used,