[texhax] What's wrong with \catcode`\_=12

[Yue Wu]

I want to define a macro to let _ can be directly used in it but failed,
The minimum failed example:

\def\mytest#1{{\chardef\_=95 \catcode`\_=12 #1}}
\mytest{foo_bar}

What should I do?

-- 
Regards,
Yue Wu

Key Laboratory of Modern Chinese Medicines
Department of Traditional Chinese Medicine
China Pharmaceutical University(中國藥科大學)
No.24, Tongjia Xiang Street, Nanjing 210009, China