placed before a selbri, merges x1 and x3 places (with the new x1 being equivalent to the result of this merging).
Causes relabelling such that all slots subsequent to x3 in the original brivla have their indices decremented by 1; for example, the original x4 becomes the new x3; notice that x2 is not altered in index or meaning. See also se'e'i, ve'e'i, xe'e'i, ze'e'i, te'e'a, ze'e'au.