Can you help me to explain a example in manual?

[receipt]

help-bison  ！

    Hello, when I was look through the man-page of bison ,I found a example :
************************************************************************************
@example
@group
stmt:   LET '(' var ')'
                @{ $<context>$ = push_context ();
                  declare_variable ($3); @}
        stmt    @{ $$ = $6;
                  pop_context ($<context>5); @}
@end group
@end example

@noindent
As soon as @samp{let (@var{variable})} has been recognized, the first
action is run.  It saves a copy of the current semantic context (the
list of accessible variables) as its semantic value, using alternative
@code{context} in the data-type union.  Then it calls
@code{declare_variable} to add the new variable to that list.  Once the
first action is finished, the embedded statement @code{stmt} can be
parsed.  Note that the mid-rule action is component number 5, so the
@samp{stmt} is component number 6.
***************************************************************************************

   I can not understand the sentence :    "Note that the mid-rule action is 
component number 5",
so can you help me on this ? I mean what does the entire action sequence look 
like ? 
 ！
                                

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　　　　　　　　　　2006-09-06