What is the right way to stop an endless while-loop with a Term::ReadLine::readline?

This way I can not read in a single 0

#!/usr/bin/env perl
use warnings; 
use strict;
use 5.010;
use Term::ReadLine;

my $term = Term::ReadLine->new( 'Text' );

my $content;
while ( 1 ) {
    my $con = $term->readline( 'input: ' );
    last if not $con;
    $content .= "$con\n";
}   
say $content;

and with

last if not defined $con;

the loop does never end.