+# (callable) Percent‐decode the given strings.
+override perdec = $(foreach encoded,$1,$(shell $(PRINTF) '%s\n' $(call quote,$(encoded)) | $(SED) 's/`/`%60`/g;s/[\]/`%5C`/g;s/%[0-9A-Fa-f]\{2\}/`&`/g' | $(TR) '`' '\n' | $(SED) '/^%[0-9A-Fa-f]\{2\}$$/!s/%/`%25`/' | $(TR) '`' '\n' | $(AWK) '$$0!~/%/{printf("%s",$$0)}/%/{sub("%","0x");printf("\\%04o",$$0)}' | $(XARGS) -0 $(PRINTF) '%b'))
+
+# (callable) Percent‐encode the given strings.
+#
+# This singly‐encodes u·r·i characters and doubly‐encodes other
+# characters, then calls `perdec´ to decode back to a single encoding.
+# The encoding assumes the input is a “u·r·i component”; e·g that the
+# resulting string should only contain `pchar´ (but can contain any
+# `sub-delim´).
+override perenc = $(foreach unencoded,$1,$(call perdec,$(shell $(PRINTF) '%s' $(call quote,$(unencoded)) | $(OD) -t x1 | $(SED) 's/^[0-9]*//;s/2[146-9A-Ea-e]/%&/g;s/3[0-9AaBbDd]/%&/g;s/40/%&/g;s/[46][1-9A-Fa-f]/%&/g;s/[57][0-9Aa]/%&/g;s/7[Ee]/%&/g;s/[ ][0-9A-Fa-f]\{2\}/%25&/g' | $(TR) -d ' \n' | $(TR) 'abcdef' 'ABCDEF')))
+
+# (callable) Percent‐encode each component in the given paths.
+override pathenc = $(foreach path,$1,$(subst $(space),/,$(call perenc,$(subst /, ,$(path)))))
+
+# (overridable) Collect all of the applicable includes from the
+# includes directory.