For me, it's the other way around. For the majority of the (sub)patterns (even with most uses of backslashes), it doesn't matter whether you write q{PAT} or qr{PAT} (it's the same keystrokes inside the braces). Meaning, there's absolutely nada difference in readability.
Why go for the expensive solution? If your pattern grows, at what moment do you revisit your program, and chop off the r in qr?
It's not that I never use qr. Sometimes, there's a (sub)pattern that's more readable as qr than as q. And sometimes, one does want a first class regexp construct. But those are the exceptions.
Do note that using q building blocks to build your patterns gives you more flexibility than limiting yourself to just qr:
my $vowels = 'aeiou';
my $odds = '13579';
my $odd_or_vowel = '[$vowels$odds]';
To write that as qr, you'd have to write something like:
my $vowels = qr/[aeiou]/;
my $odds = qr/[13579]/;
my $odd_or_vowel = qr/$vowels|$odds/;
which, while matching the same language, throws off the optimizer, and makes not only for a slower compilation, the match itself is slower. | [reply]
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