x["aaa"]=111; x["bbb"]=222; x["ccc"]=333;
if (val in ("aaa","bbb","ccc") )
$ nawk 'BEGIN {x["aaa"]=111;x["bbb"]=222;x["ccc"]=333} {if ($1 in x) print x[$1]}' aaa 111 bbb 222 ccc 333 ddd ^C $