This is a nice way to improve efficiency of all shell scripts.
Bash shell programmers can improve the efficiency of their scripts by using the shell’s dynamically loadable built-in commands. Chris F.A. Johnson shows us how to use them.
FTA “…If you use the shell for serious programming, as I do, speed of execution is a serious issue. A script should not appear sluggish; it should not be noticeably slower than a program written in Perl or Python  or even C. One of the major contributors to slowdown of scripts is starting a new process, whether it is an external command or command substitution. (All shells except Korn Shell 93 create a new process for command substitution.)…”