switch ($month) 
{
        case [1]    {$mon="Jan"}
        case [2]    {$mon="Feb"}
        case [3]    {$mon="Mar"}
        case [4]    {$mon="Apr"}
        case [5]    {$mon="May"}
        case [6]    {$mon="Jun"}
        case [7]    {$mon="Jul"}
        case [8]    {$mon="Aug"}
        case [9]    {$mon="Sep"}
        case [10]    {$mon="Oct"}
        case [11]    {$mon="Nov"}
        case [12]    {$mon="Dec"}
}

##</code><code>##

$mon = (qw(Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec))[$month-1];