BINDING CALLBACKS AND SUBSTITUTIONS
    The *callback* argument to bind is a perl/Tk callback. which will 
+be
    executed whenever the given event sequence occurs. (See Tk::callba
+cks
    for description of the possible forms.) *Callback* will be associa
+ted
    with the same MainWindow that is associated with the *$widget* tha
+t was
    used to invoke the bind method, and it will run as though called f
+rom
    MainLoop. If *callback* contains any Ev(*%*) calls, then each "nes
+ted"
    Ev(*%*) "callback" will be evaluated when the event occurs to form
    arguments to be passed to the main *callback*. The replacement dep
+ends
    on the character *%*, as defined in the list below. Unless otherwi
+se
    indicated, the replacement string is the numeric (decimal) value o
+f the
    given field from the current event. Perl/Tk has enhanced this mech
+anism
    slightly compared to the comparable Tcl/Tk mechanism. The enhancem
+ents
    are not yet all reflected in the list below. Some of the substitut
+ions
    are only valid for certain types of events; if they are used for o
+ther
    types of events the value substituted is undefined (not the same a
+s
    undef!).

    '#' The number of the last client request processed by the server 
+(the
        *serial* field from the event). Valid for all event types.

    'a' The *above* field from the event, formatted as a hexadecimal n
+umber.
        Valid only for Configure events.

    'b' The number of the button that was pressed or released. Valid o
+nly
        for ButtonPress and ButtonRelease events.

    'c' The *count* field from the event. Valid only for Expose events
+.

    'd' The *detail* field from the event. The 'd' is replaced by a st
+ring
        identifying the detail. For Enter, Leave, FocusIn, and FocusOu
+t
        events, the string will be one of the following:

         NotifyAncestor          NotifyNonlinearVirtual
         NotifyDetailNone        NotifyPointer
         NotifyInferior          NotifyPointerRoot
         NotifyNonlinear         NotifyVirtual

        For ConfigureRequest events, the string will be one of:

         Above                   Opposite
         Below                   None
         BottomIf                TopIf

        For events other than these, the substituted string is undefin
+ed.
        (Note that this is *not* the same as Detail part of sequence u
+se to
        specify the event.)

    'f' The *focus* field from the event (0 or 1). Valid only for Ente
+r and
        Leave events.

    'h' The *height* field from the event. Valid only for Configure,
        ConfigureRequest, Create, Expose, and ResizeRequest events.

    'i' The window field from the event, represented as a hexadecimal
        integer.

    'k' The *keycode* field from the event. Valid only for KeyPress an
+d
        KeyRelease events.

    'm' The *mode* field from the event. The substituted string is one
+ of
        NotifyNormal, NotifyGrab, NotifyUngrab, or NotifyWhileGrabbed.
+ Valid
        only for Enter, FocusIn, FocusOut, and Leave events.

    'o' The *override_redirect* field from the event. Valid only for M
+ap,
        Reparent, and Configure events.

    'p' The *place* field from the event, substituted as one of the st
+rings
        PlaceOnTop or PlaceOnBottom. Valid only for Circulate and
        CirculateRequest events.

    's' The *state* field from the event. For ButtonPress, ButtonRelea
+se,
        Enter, KeyPress, KeyRelease, Leave, and Motion events, a decim
+al
        string is substituted. For Visibility, one of the strings
        VisibilityUnobscured, VisibilityPartiallyObscured, and
        VisibilityFullyObscured is substituted.

    't' The *time* field from the event. Valid only for events that co
+ntain
        a *time* field.

    'w' The *width* field from the event. Valid only for Configure,
        ConfigueRequest, Create, Expose, and ResizeREquest events.

    'x' The *x* field from the event. Valid only for events containing
+ an
        *x* field.

    'y' The *y* field from the event. Valid only for events containing
+ a *y*
        field.

    '@' The string "@*x,y*" where *x* and *y* are as above. Valid only
+ for
        events containing *x* and *y* fields. This format is used my m
+ethods
        of Tk::Text and similar widgets.

    'A' Substitutes the UNICODE character corresponding to the event, 
+or the
        empty string if the event doesn't correspond to a UNICODE char
+acter
        (e.g. the shift key was pressed). XmbLookupString does all the
+ work
        of translating from the event to a UNICODE character. Valid on
+ly for
        KeyPress and KeyRelease events.

    'B' The *border_width* field from the event. Valid only for Config
+ure,
        ConfigureRequest and Create events.

    'D' This reports the delta value of a MouseWheel event. The delta 
+value
        represents the rotation units the mouse wheel has been moved. 
+On
        Windows 95 & 98 systems the smallest value for the delta is 12
+0.
        Future systems may support higher resolution values for the de
+lta.
        The sign of the value represents the direction the mouse wheel
+ was
        scrolled.

    'E' The *send_event* field from the event. Valid for all event typ
+es.

    'K' The keysym corresponding to the event, substituted as a textua
+l
        string. Valid only for KeyPress and KeyRelease events.

    'N' The keysym corresponding to the event, substituted as a decima
+l
        number. Valid only for KeyPress and KeyRelease events.

    'R' The *root* window identifier from the event. Valid only for ev
+ents
        containing a *root* field.

    'S' The *subwindow* window identifier from the event, as an object
+ if it
        is one otherwise as a hexadecimal number. Valid only for event
+s
        containing a *subwindow* field.

    'T' The *type* field from the event. Valid for all event types.

    'W' The window to which the event was reported (the $widget field 
+from
        the event) - as an perl/Tk object. Valid for all event types.

    'X' The *x_root* field from the event. If a virtual-root window ma
+nager
        is being used then the substituted value is the corresponding
        x-coordinate in the virtual root. Valid only for ButtonPress,
        ButtonRelease, KeyPress, KeyRelease, and Motion events.

    'Y' The *y_root* field from the event. If a virtual-root window ma
+nager
        is being used then the substituted value is the corresponding
        y-coordinate in the virtual root. Valid only for ButtonPress,
        ButtonRelease, KeyPress, KeyRelease, and Motion events.
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