# Possibly unused \`extra\` field in \`Regex\` struct

**URL:** <https://discourse.julialang.org/t/possibly-unused-extra-field-in-regex-struct/10479>\
**Category:** Internals & Design\
**Created:** [April 22, 2018, 12:24pm UTC](https://discourse.julialang.org/t/possibly-unused-extra-field-in-regex-struct/10479 "2018-04-22T12:24:16Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![ScottPJones](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/scottpjones/32/146_2.png) [@ScottPJones](https://discourse.julialang.org/u/ScottPJones)\
**Post date:** [April 22, 2018, 12:24pm UTC](https://discourse.julialang.org/t/possibly-unused-extra-field-in-regex-struct/10479/1 "2018-04-22T12:24:16Z")

</div>

There is a field `extra::Ptr{Void}` in the `Regex` struct in `julia/base/regex.jl`.  
I was wondering if anybody knew what it was for, as it doesn’t seem to be used at all in the Julia code, and doesn’t seem to be in the PCRE API.  
Thanks!