The final phrase has a dual meaning

but the second meaning you describe does not apply since it makes no sense thinking that

use strict 'refs';
[download]

might be declared by accident.

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}

asserting that "the final phrase has a dual meaning... " means that "this feature" can be properly interpreted as " use strict 'refs'", and so the sentence can properly be re-written as "The declaration  use strict 'refs' disables  use strict 'refs', which can cause all sorts of trouble if you use it by accident."     this is clearly not the case (if one is paying attention).

You filled in an absurd ambiguity, and proceeded to demonstrate that the the ambiguity was absurd. But that was not the interpretation I meant. Ah the joys of English. Perl is better (even though it is probably the most ambiguous computer language I know of).

When I say ambiguity I mean that the original sentence can be read as:

"The declaration use strict 'refs' disables this feature. This disabling can cause all sorts trouble..."

b4swine:

Pronoun useage, like the rest of the English language, has what amount to "undocumented features," introduced by shifts, abuse and regionalisms, so this is DEFINITELY NOT to say you're wrong. And, note, FWIW, neither of the cited passages below comes from an "ultimately authoratative source" (it's really hard to cut and paste from a dead-trees copy of OED, and even if one did so, one could find respectable disagreements, sometimes).

With those caveats, however, this from http://www.answers.com/topic/which:

USAGE NOTE The relative pronoun which is sometimes used to refer to an entire sentence or clause, rather than a noun or noun phrase, as in She ignored him, which proved to be unwise. They swept the council elections, which could never have happened under the old rules. While these examples are unexceptionable, using which in this way sometimes produces an ambiguous sentence. Thus It emerged that Edna made the complaint, which surprised everybody leaves unclear whether it was surprising that a complaint was made or that Edna made it. The ambiguity can be avoided with paraphrases such as It emerged that the complaint was made by Edna, a revelation that surprised everybody. • Which may be used to refer to an entire sentence or clause only when it is preceded by that sentence or clause. When the referent follows, what should be used, particularly in formal style: Still, he has not said he will withdraw, which is more surprising but Still, what (not which) is more surprising, he has not said he will withdraw. See Usage Notes at that, what, whose.

Conversely (in part), from http://www.yourdictionary.com/which:

1. what one (or ones) of the number of persons, things, or events mentioned or implied? which of the men answered? which do you want?
2. the one (or ones) that he knows which he wants
3. that: used as a relative referring to the thing, group, or event specified in the antecedent word, phrase, or clause: which can be used in a restrictive clause the war which had just ended, the class to which he spoke, in a restrictive clause preceded by the pronoun that [he sacrificed that which he valued most], in a nonrestrictive clause [my car, which is not running; my family, in which she found a warm welcome], or, archaically, of a person [Our Father, which art in heaven]
4. either, or any, of the persons, things, or events previously mentioned or implied; whichever take which you prefer
5. a thing or fact that you are late—which reminds me, where were you yesterday?

Short-form synopsis: The occupant of this seat disagrees with your use of "absurd" but aknowledges some linguistic merit.

update: Typo fixed; s/had/hard/ in para 1

otoh, ambiguity in language is the basis of much, perhaps most, humor, so maybe this is b4swine's joke.