/usr/lib/ghc-doc/hoogle/regexpr.txt is in libghc-regexpr-doc 0.5.4-5build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-regexpr-doc/html/regexpr.txt
/usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-regexpr-doc/html/regexpr.txt