while ( $sth->fetch() )
{
      chomp $x;
      if ( $x =~ /^foo/ ) {
        print "$x\n";
        last;
      }
}

##</code><code>##

my ($count) = $dbh->selectrow_array("SELECT count(*) FROM table WHERE LEFT(colum,3) = 'foo'");
if ($count > 0) {
   print "Do what you need here";
}