&gt;&gt; Just ask the Python and Perl teams.<p>&gt; Python and Perl were not backwards compatible with anything when they were released.<p>I think the implication is that the teams will tell you that the upgrades to Python 3 and Perl 6 were problematic because they didn&#x27;t offer backwards compatibility.  If so, it&#x27;s a bit silly, because the point of those upgrades was to advance the languages beyond would could be done with backwards compatible iteration. Asking the <i>teams</i> would probably yield a bunch of people that were adamant that the decision was sound, and it needed to be done, but there were missteps in execution.  Asking the <i>communities</i> would likely yield a more polarized set of opinions.<p>That said, IMO using either of these items as examples to bolster an argument is almost always a mistake, since their own discussions are so large and polarizing, they rarely ever make make a point <i>more</i> clear.