That snake in the grass reported me to the boss.　

KEY & NOTES:

那個口蜜腹劍的家伙到老板那里告了我一狀。

沒錯吧，＂藏在草叢中的蛇＂就是那種＂偽裝成朋友的很陰險的人＂
（someone who pretends to be your friend while secretly doing
things to harm you ）！這樣的人，往往容易被忽略，卻是最可怕的，
所以我們一定要慧眼識人！把敵人當朋友，那可是件很傷心很痛苦的事情．
It's upsetting to learn that someone you once viewed as a good
colleague is in fact a snake in the grass.^_^