Ouh, I just forgot to post it! I I found how to write it, thanks a lot!
Here is an example :

use Tkx;

Tkx::package_require('tooltip');
Tkx::namespace_import("::tooltip::tooltip");


my $mw = Tkx::widget->new(".");

my $nameDTDlbl = $mw->new_ttk__label(-text => "The following entry wid
+get got a tooltip :");
$nameDTDlbl->g_grid( -column => 0, -row => 0, -sticky => "we", -pady=>
+5);
my $nameDTDcase= $mw->new_ttk__entry(-width => 35,);
$nameDTDcase->g_grid( -column => 0, -row => 1, -sticky => "w", -padx=>
+10, -pady => "0 3");
Tkx::tooltip($nameDTDcase, "Example : \"tei_corpus.dtd\"");

Tkx::MainLoop();
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