$ ls .ghc
ls: cannot access '.ghc': No such file or directory

$ ghci
GHCi, version 9.8.2: https://www.haskell.org/ghc/  :? for help
Loaded GHCi configuration from /home/mikko/dotfiles/ghc/.config/ghc/ghci.conf

λ: import Text.Regex.Posix

<no location info>: error: [GHC-35235]
    Could not find module ‘Text.Regex.Posix’.
    It is not a module in the current program, or in any known package.

λ: 
Leaving GHCi.

$ cabal install --lib regex-posix
Resolving dependencies...

$ ls .ghc
x86_64-linux-9.8.2

$ ghci
Loaded package environment from /home/mikko/.ghc/x86_64-linux-9.8.2/environments/default
GHCi, version 9.8.2: https://www.haskell.org/ghc/  :? for help
ghci> import Text.Regex.Posix
ghci> 
Leaving GHCi.

$ rm -rf .ghc

$ ghci
GHCi, version 9.8.2: https://www.haskell.org/ghc/  :? for help
Loaded GHCi configuration from /home/mikko/dotfiles/ghc/.config/ghc/ghci.conf

λ: import Text.Regex.Posix

<no location info>: error: [GHC-35235]
    Could not find module ‘Text.Regex.Posix’.
    It is not a module in the current program, or in any known package.

λ: 
Leaving GHCi.