The values sent by the variable {{LANGUAGE}} are encoded with the ISO 639-1 format, find a few examples of the supported languages as follows :
EN
FR
ES
IT
DE
JP
ZH
AR
BG
HR
CS
DA
NL
FI
EL
HE
HU
KO
NO
PL
PT
RO
RU
SR
SK
SL
SV
TH
TR
VI
Any other language will send the EN code (English).
A complete list is available on the ISO 639-1 format's Wikipedia Entry !