Could you give an actual code example, i'm not sure what you're saying. It appears from the MySQL documentation that the ENCODE function requires 2 parameters, but you haven't mentioned that. Anyway, likely the best way is to just connect to MySQL and perform the operation, for example:

use strict;
use warnings;
use DBI;
my $dsn = 'DBI:mysql:host=localhost';
my $dbh = DBI->connect($dsn);
my $sth = $dbh->prepare("SELECT DECODE('encodedcontent', 'secretvalue'
+)");
$sth->execute;
my $decoded = $sth->fetchrow;
print $decoded;
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There is problem: SELECT ENCODE('test','test') returns ?üÔÚ but SELECT DECODE('?üÔÚ','test') doesn't return test but ttZ¦ô what is wrong ?

Really can't say. Maybe a character encoding problem if you're copy-and-pasting. The following code works here:

use strict;
use warnings;
use DBI;
my $db = DBI->connect('DBI:mysql:host=localhost');
my ($encoded) = $db->selectrow_array("SELECT ENCODE('ToBeHidden', 'sec
+retvalue')");
my ($decoded) = $db->selectrow_array("SELECT DECODE('$encoded', 'secre
+tvalue')");
print $decoded;   # prints --> ToBeHidden
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