meaning of @variablename@

[Arun Jain]

Hello Group,

I am new to this utility (automake).  I am working on Linux platform with
KDE libraries.  I came across some variable names
in the makefile such as

@SET_MAKE@
srcdir = @srcdir <address@hidden>@
top_srdcdir = @top_srcdir@
etc.

My question is;

1.  Do the variable names under two @ signs have any special meaning in
automake.
2.  If not can I use two @ for any variable name.
3.  What does automake convey/mean when someone wraps a variable name in two
@.
4.  Are there some special variables like "SET_MAKE", which always have
special meaning.

Could someone help me.

Thanks.

nagrik