The languages are much more similar than they are different (in terms of feature set, not mindset), but one thing perl has which I don't understand how the pyth

The languages are much more similar than they are different (in terms of feature set, not mindset), but one thing perl has which I don't understand how the python+ruby people get by without is 'use strict'. (ObLanguageWar: I'm not trying to promote perl here - I know the other languages have particular features perl does not - I'm just curious about this specific item.) Every sane perl programmer will have this pragma enabled, and it requires you to declare lexical variables, otherwise you get a compile-time error. I understand (please correct me if I'm wrong) that python+ruby instead allow lexicals to be created by assignement, leading to this problem: def important_condition(): return 1 FOO = "wrong" if important_condition(): FO0 = "correct" print FOO I'm told there are lint-like tools for python which can catch this, but since people typically don't use Makefiles to manage their python/perl/ruby code I can't imagine they are routinely used on each edit/run cycle. Can any python/ruby coders comment on this? Is it an error case which takes any significant debugging time? (Rather than the O/0 distinction above, I see this sort of error more often from inConsistent camelCase).