Shell script that runs command with network proxy variables

proxied.sh

#!/bin/bash -e
HELP_STR="\
Usage:
        proxied                   # prints this message
        proxied _proxy_           # prints sh snippet that sets _proxy_
        proxied _proxy_ _cmd_...  # runs _cmd_ with _proxy_

Environment variables that are affected:
     -  ALL_PROXY
     -  http_proxy
     -  https_proxy

"

case "$#" in
    0)
        printf '%s' "$HELP_STR"
        ;;
    1)
        echo "export ALL_PROXY='$1';"
        echo "export http_proxy='$1';"
        echo "export https_proxy='$1';"
        ;;
    *)
        (eval "$("$SHELL" "$0" "$1")" && shift && "$@";)
        ;;
esac