Switching back to the previous application with AppleScript

If you want to simulate cmd + tab with AppleScript, here it is

tell application "System Events"
  tell process "finder"
    activate
    keystroke tab using {command down}
  end tell
end tell

You can use the same thing in bash

echo 'tell application "System Events"
  tell process "finder"
    activate
    keystroke tab using {command down}
  end tell
end tell' | osascript