regsub(n) on macOS
The text 004504e9835f, as Mac OS X 10.4.2, Mac OS X 10.4.1, Mac OS X 10.4 shipped it.
Perform substitutions based on regular expression pattern matching
Flags it lists
-
-- -
-all -
-expanded -
-line -
-lineanchor -
-linestop -
-nocase -
-start