Tcl/Tk works on Wayland compositors through Xwayland. The contents of the Xwayland clipboard vanish when the application the content was copied from is closed, so this snippet executes wl-copy if the session is Wayland.
bind .copiable <Button-1> { global env if { $env(XDG_SESSION_TYPE) == "wayland" } { exec wl-copy "Copied! (Wayland)" } else { clipboard append "Copied! (X11)" } }