the above recommendations are probably better (i'm not looking at the dbi page right now, might say the same thing), but here's what i do:

my $select =   qq/SELECT * /;
my $from =     qq/FROM db/;

my $query = $select . $from;


#  print "SQL: $query\n";
   my $sth = $dbh->prepare( $query );
   $sth->execute;
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note the print statement. also, it's not secure in any way - just for testing. also, iirc the perl taint doesn't effect dbi data - separate taint.