Use a local for format like the other functions

.github/sh/library/variables.inc.sh

@@ -4,7 +4,7 @@
 set_sl_var() { local f='%s=%s\n' ; printf -- "${f}" "$@" ; } ;
 
 # Used together to set multiple line variables in the environment or output
-mk_delim() { printf -- '"%s_EOF_%d_"' "$1" "${RANDOM}" ; } ;
+mk_delim() { local f='%s_EOF_%d_' ; printf -- "${f}" "$1" "${RANDOM}" ; } ;
 open_ml_var() { local f=''\%'s<<'\%'s\n' ; printf -- "${f}" "$2" "$1" ; } ;
 close_ml_var() { local f='%s\n' ; printf -- "${f}" "$1" ; } ;