WHERE ... AND ((CLName LIKE 'A%') OR (CLName in ('MET-CL1','BDO-CL1'))

##</code><code>##

if ($clnm) {
  @parts = split /,/,$clnm;
  map { m/\'\w\'/ ? push @pre, $_ : push @words, $_ } @parts;

##</code><code>##

 $in_clause = sprintf "( CLName IN (%s) )", join ',',@words;