Gist
"Intact Case" is the rules for mutual conversion camel case and underscore notation. It enables interconversion intactly camel case and snake_case, even if compound words contain acronym.
Libraries
We have created libraries for mutual conversion of camelCase and snake_case in rules of Intact Case.
Notes of Regular Expression
This is the research on regular expressions that I noticed in the library during the creation of the Intact Case.