Info-following-node-name-re is a compiled Lisp function in `
(Info-following-node-name-re &optional ALLOWEDCHARS)
Return a regexp matching a node name.
ALLOWEDCHARS, if non-nil, goes within [...] to make a regexp
saying which chars may appear in the node name.
Submatch 1 is the complete node name.
Submatch 2 if non-nil is the parenthesized file name part of the node name.
Submatch 3 is the local part of the node name.
End of submatch 0, 1, and 3 are the same, so you can safely concat.