Here are (single-file) eggs for SRFI-85, recursive equivalence procedures,
and SRFI-95, simple sort-merge. SRFI-85 has been withdrawn, but there's
nothing wrong with it: it provides R6RS-style equality of infinite trees
under the name of "equiv?", and directed acyclic graph equality under
the name of "dag-equiv?"
SRFI-95 provides the same five procedures as Chicken's built-in "sorted?",
"sort", "sort!", "merge", and "merge!" procedures. However, an optional
key argument can be provided. In addition, "sorted?", "sort", and
"sort!" can accept strings and SRFI-63 general arrays as well as lists
and vectors.
The srfi-95 egg depends on the array-lib egg.