nixpkgs/pkgs/development/interpreters/guile/setup-hook-2.0.sh

addGuileLibPath () {
    if test -d "$1/share/guile/site/2.0"
    then
        export GUILE_LOAD_PATH="${GUILE_LOAD_PATH}${GUILE_LOAD_PATH:+:}$1/share/guile/site/2.0"
        export GUILE_LOAD_COMPILED_PATH="${GUILE_LOAD_COMPILED_PATH}${GUILE_LOAD_COMPILED_PATH:+:}$1/share/guile/site/2.0"
    elif test -d "$1/share/guile/site"
    then
        export GUILE_LOAD_PATH="${GUILE_LOAD_PATH}${GUILE_LOAD_PATH:+:}$1/share/guile/site"
        export GUILE_LOAD_COMPILED_PATH="${GUILE_LOAD_COMPILED_PATH}${GUILE_LOAD_COMPILED_PATH:+:}$1/share/guile/site"
    fi
}

envHooks+=(addGuileLibPath)