Self documenting Bash script

self_help.sh

#!/usr/bin/env bash

if [[ ${*} =~ help|-h || ${#} == 0 ]]; then cat <<HELP_USAGE | sed "s/^#? //"
#? USAGE
#? ======
#? Anywhere in your script:
#? 
#?    if [[ $* =~ help|-h || $# == 0 ]]; then cat <<HELP_USAGE | sed "s/^#? //"
#?    #? Documentation lines prefixed with '#? '
#?    HELP_USAGE
#?    exit 0; fi
#? 
#? FEATURES
#? ========
#? * Preformatted.
#? * Variable expansion: \${HOME} is '${HOME}'
#? * Commands can be executed
#?    '\$(echo Foo)' results in '$(echo Foo)'
#? * Script being documented can self referenced
#?   '\${0}' => '${0}'
#? 
HELP_USAGE
exit 0; fi