-- set theUsername to "my@example.org"
-- set thePassword to "mybirthday"

tell application "Safari"
    set theWindow to front window
    set theTabs to theWindow's tabs --of every window
    repeat with eachTab in theTabs
        -- send current URL to instapaper
        set theInstapaperResult to do shell script "curl "https://www.instapaper.com/api/add?username=" & theUsername & "&password=" & thePassword & "&url=" & URL of eachTab & """
        if theInstapaperResult is "403" then
            display dialog "Seems like your username / password doesn't match" buttons ("Continue") default button 1 with icon stop
            return
        else
            if theInstapaperResult is not "201" then
                display dialog "Something went wrong, I'm not sure what at this moment" buttons ("Continue") default button 1 with icon stop
                return
            end if
        end if
        close eachTab
    end repeat

    -- if the window wasn't closed by closing the last tab, close it now :)
    if theWindow exists then
        close theWindow
    end if

end tell