virtualenvwrapper hooks to cleanly set/restore some variables when activating/deactivating a venv

postactivate.sh

#!/bin/sh
# This hook is sourced after every virtualenv is activated.

__vew_is_in_env () {
    awk 'BEGIN { exit ! ("'"$1"'" in ENVIRON) }'
}

__vew_set_and_preserve () {
    if __vew_is_in_env "$1" && ! __vew_is_in_env "__VEW_OLD_$1"; then
        eval "__VEW_OLD_$1=\$$1"
        export "__VEW_OLD_$1"
    fi

    eval "$1=$2"
    export "$1"
}

__vew_project_dir=$(cat "$VIRTUAL_ENV/$VIRTUALENVWRAPPER_PROJECT_FILENAME")

if [ -d "$__vew_project_dir" ]; then
    if [ -f "$VIRTUAL_ENV/.perl6" ]; then
        __vew_set_and_preserve "PERL6LIB" "$__vew_project_dir/lib"
    fi
    if [ -f "$VIRTUAL_ENV/.perl5" ]; then
        __vew_set_and_preserve "PERL5LIB" "$__vew_project_dir/lib"
    fi
    if [ -f "$VIRTUAL_ENV/.perl" ]; then
        __vew_set_and_preserve "PERLLIB" "$__vew_project_dir/lib"
    fi
fi

unset -v __vew_project_dir
unset -f __vew_set_and_preserve
unset -f __vew_is_in_env

predeactivate.sh

#!/bin/sh
# This hook is sourced before a virtualenv is deactivated.

__vew_is_in_env () {
    awk 'BEGIN { exit ! ("'"$1"'" in ENVIRON) }'
}

__vew_restore_and_unset () {
    if __vew_is_in_env "__VEW_OLD_$1"; then
        eval "$1=\$__VEW_OLD_$1"
        export "$1"
        unset "__VEW_OLD_$1"
        export "__VEW_OLD_$1"
    else
        unset "$1"
        export "$1"
    fi
}

__vew_project_dir=$(cat "$VIRTUAL_ENV/$VIRTUALENVWRAPPER_PROJECT_FILENAME")

if [ -d "$__vew_project_dir" ]; then
    if [ -f "$VIRTUAL_ENV/.perl6" ]; then
        __vew_restore_and_unset "PERL6LIB"
    fi
    if [ -f "$VIRTUAL_ENV/.perl5" ]; then
        __vew_restore_and_unset "PERL5LIB"
    fi
    if [ -f "$VIRTUAL_ENV/.perl" ]; then
        __vew_restore_and_unset "PERLLIB"
    fi
fi

unset -v __vew_project_dir
unset -f __vew_set_and_preserve
unset -f __vew_is_in_env