Well, apparently it is working...
I feel silly, shouldn't have posted for this...

#!/usr/bin/perl 

use warnings;
use Term::ReadLine;
use Tk;

$mw = MainWindow->new;
$mw->geometry('500x400');
$mw->title ("Title");


my $term = new Term::ReadLine 'Perl shell';
my $OUT = $term->OUT || \*STDOUT;
$term->tkRunning(1);

while ( defined ($_ = $term->readline('Poil Shell >')) ) {
    my $res = eval($_);
    warn $@ if $@;
}
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