The pipe symbol is not such a problem with m|some pattern| as the pipes are at either end but when substituting like s|old|new| it's the one in middle that causes the double-take. Like you I've not been bitten by it but it does cause me that moment of hesitation.

I used to use pipe symbols a lot but I find that I am wearing out the curly brace keys as I tend towards m{...} and s{...}{...} these days. It might have something to do with my addiction to quoting constructs. :)

Cheers,

JohnGG