Or as I said before, make Control-V| input the sequence 0x16|.
Escaping <literal-next> with <literal-next> will produce the <literal-next> character, which is CH_LITERAL, 0x16. So the sequence "Control-VControl-V|" in edit mode will produce a valid | for a mapping as typing one in a :map command and saving it with :mkexrc. Looking at the code, just documenting this seems to be the best option. End of my monologue. adr