[Deque]

Also, the manual you're referring to is the manual for GAWK (GNU AWK), which is a very similar dialect of the AWK language, but not always analog.

GNU AWK is not a dialect, it's one of the main language implementations of AWK. It just provides some more features than the AWK specification requires. That means everything that is AWK works with GNU AWK. The guide covers both: AWK as specified in POSIX and GAWK specific features.