Japanese text search problem

Hi all,

We are trying to search japanese keyword using a search string(in perl using 
pattern matching).
We are facing problem while searching a particular keyword as given below,
$searchStr =~ m/$key1/i

when $key1 contains シリーズ
We get an error as follows

/シリーズ/: unmatched [] in regexp 

Please suggest the solution to overcome the problem.

Thanks,

Ashutosh.