Indeed, he spelled it the right way, which is the wrong way. He should spell it wrong, which is the right way. :)
I think it is funny that this misspelling hasn't been fixed after all of these years. It was typo'ed in the original http spec in 1996: https://en.wikipedia.org/wiki/HTTP_referer
If the web server is following RFC 8969, it will treat "referrer" as "referer" and throw a 397 TOLERATING to let you know you should change it to the latter on your end. See Section 3.
There are regional variations in the use of doubled or single consontants:
UK: travelling, signalling
USA: traveling, signaling
The double l serves no purpose in these.
However, there is no such UK/USA split in "referring": both use double "r".
There is a phonetic reason for that which is that the second syllable has the emphasis in "refer", unlike "traveling" and "signaling" where the leading syllable has it.
The double "rr" indicates the stressed syllable, without which "refering" and "referer" could be misread with emphasis on the first syllable, like "buffering" or "suffering"/"sufferer".
A native speaker with good intuition for spelling would never write "refering" or "referrer", even if they find "signaling" acceptable.
I think most non-perishable goods are the same across stores. There are regional differences between some perishable goods based on where they come from.
Yes, you make a good point. Although I suspect there may be regional differences in price, I haven't yet run the diff on that. Should be simple enough for me to allow the user to select their regional store location.
This is not correct as stated. It does not “tend towards extremes” as you might expect intuitively. That would be the case if half the time it approached 100% blue and half the time it approached 100% red, which is precisely not what happens.