Rebol[]

clipboard-content: []

view layout [
    box "Click or Right-Click" forest feel [
        engage: func [face action event] [

                if (action = 'up) [append clipboard-content join "<img src=" [x: read clipboard:// ">" newline]
                    print x
                ]
                if (action = 'alt-up) [write clipboard:// form clipboard-content
                    print clipboard-content
                ]
        ]
    ]
]