Why can't I use integer called "AS2" in my program?

Other Hardware Robotics
1 
In file included from c:\program files (x86)\arduino\hardware\tools\avr\avr\include\avr\iom2560.h:38:0,

                from c:\program files (x86)\arduino\hardware\tools\avr\avr\include\avr\io.h:174,

                from c:\program files (x86)\arduino\hardware\tools\avr\avr\include\avr\pgmspace.h:88,

                from C:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino/Arduino.h:28,

                from sketch\multiple_color_sensor_test.ino.cpp:1:

multiple_color_sensor_test:4: error: expected unqualified-id before numeric constant

int AS2 = 22;

    ^

exit status 1
expected unqualified-id before numeric constant

This is the error message that I'm getting from my little project. However, this is so strange, because when I do anything else than "AS2" that code works perfectly fine. Like "aS2," "BS2," etc. Do you guys know what happened to me? There is my code file in case you need it. Thanks for your contribution to my topic:)

multiple_color_sensor_test.ino (1.25 KB)

2

Its a #define for one of the bits in the ASSR register.

3 
#ifdef AS2
#undef AS2
#endif