Prefix `_debug` strings with '•' to avoid highlighting bugs.

GitHub's syntax highlighting doesn't work well when strings contain
function names with parentheses, so add character to the beginning of
the string to see whether this makes it better.

hosts

@@ -311,8 +311,8 @@ _DEFINED_COMMANDS=()
 # Loads all of the commands sourced in the environment.
 _load_commands() {
 
-  _debug printf "_load_commands(): entering...\n"
-  _debug printf "_load_commands() declare -F:\n%s\n" "$(declare -F)"
+  _debug printf "• _load_commands(): entering...\n"
+  _debug printf "• _load_commands() declare -F:\n%s\n" "$(declare -F)"
 
   # declare is a bash built-in shell function that, when called with the '-F'
   # option, displays all of the functions with the format
@@ -327,7 +327,7 @@ _load_commands() {
     local function_name
     function_name=$(printf "%s" "${c}" | awk '{ print $3 }')
 
-    _debug printf "_load_commands() \${function_name}: %s\n" "${function_name}"
+    _debug printf "• _load_commands() \${function_name}: %s\n" "${function_name}"
 
     # Add the function name to the $_DEFINED_COMMANDS array unless it starts
     # with an underscore or is one of the desc(), debug(), or die() functions,
@@ -360,8 +360,8 @@ _load_commands() {
 #
 # NOTE: must be called at end of program after all commands have been defined.
 _main() {
-  _debug printf "main(): entering...\n"
-  _debug printf "main() \${_CMD} (upon entering): %s\n" "${_CMD}"
+  _debug printf "• main(): entering...\n"
+  _debug printf "• main() \${_CMD} (upon entering): %s\n" "${_CMD}"
 
   # If $_CMD is blank, then set to `$HOSTS_DEFAULT_COMMAND`
   if [[ -z ${_CMD} ]]
@@ -425,10 +425,10 @@ _contains() {
   local test_list=(${*:2})
   for _test_element in "${test_list[@]:-}"
   do
-    _debug printf "_contains() \${_test_element}: %s\n" "${_test_element}"
+    _debug printf "• _contains() \${_test_element}: %s\n" "${_test_element}"
     if [[ "${_test_element}" == "${1}" ]]
     then
-      _debug printf "_contains() match: %s\n" "${1}"
+      _debug printf "• _contains() match: %s\n" "${1}"
       return 0
     fi
   done
@@ -546,10 +546,10 @@ desc() {
     read -r -d '' "_desc_${1}" <<HEREDOC
 ${2}
 HEREDOC
-    _debug printf "desc() set with argument: _desc_%s\n" "${1}"
+    _debug printf "• desc() set with argument: _desc_%s\n" "${1}"
   else
     read -r -d '' "_desc_${1}"
-    _debug printf "desc() set with pipe: _desc_%s\n" "${1}"
+    _debug printf "• desc() set with pipe: _desc_%s\n" "${1}"
   fi
   set -e
 }
@@ -706,9 +706,9 @@ Description:
   Add a given IP address and hostname pair, along with an optional comment.
 HEREDOC
 add() {
-  _debug printf "add() \${1}: %s\n" "${1:-}"
-  _debug printf "add() \${2}: %s\n" "${2:-}"
-  _debug printf "add() \${3}: %s\n" "${3:-}"
+  _debug printf "• add() \${1}: %s\n" "${1:-}"
+  _debug printf "• add() \${2}: %s\n" "${2:-}"
+  _debug printf "• add() \${3}: %s\n" "${3:-}"
 
   _verify_write_permissions "$@"
   local ip=${1:-}
@@ -796,7 +796,7 @@ disable() {
     ${_ME} help disable
     exit 1
   else
-    _debug printf "disable() \${search_string}: %s\n" "${search_string}"
+    _debug printf "• disable() \${search_string}: %s\n" "${search_string}"
 
     target_regex_ip="^\(${search_string}[${_TAB_SPACE_}]..*\)$"
     target_regex_commented_hostname="^\([^#]..*[${_TAB_SPACE_}]${search_string}[${_TAB_SPACE_}]..*\)$"
@@ -814,7 +814,7 @@ disable() {
         -e "s/${target_regex_hostname}/\1/p" \
         "${HOSTS_PATH}"
     )
-    _debug printf "disable() \${targets}: %s\n" "${targets}"
+    _debug printf "• disable() \${targets}: %s\n" "${targets}"
     if [[ -z "${targets}" ]]
     then
       _die printf "Not found: %s\n" "${search_string}"
@@ -882,7 +882,7 @@ enable() {
     ${_ME} help enable
     exit 1
   else
-    _debug printf "enable() \${search_string}: %s\n" "${search_string}"
+    _debug printf "• enable() \${search_string}: %s\n" "${search_string}"
 
     target_regex_ip="^\#disabled: \(${search_string}[${_TAB_SPACE_}]..*\)$"
     target_regex_commented_hostname="^\#disabled: \(..*[${_TAB_SPACE_}]${search_string}[${_TAB_SPACE_}]..*\)$"
@@ -900,7 +900,7 @@ enable() {
         -e "s/${target_regex_hostname}/\1/p" \
         "${HOSTS_PATH}"
     )
-    _debug printf "enable() \${targets}: %s\n" "${targets}"
+    _debug printf "• enable() \${targets}: %s\n" "${targets}"
     if [[ -z "${targets}" ]]
     then
       _die printf "Not found: %s\n" "${search_string}"
@@ -1008,8 +1008,8 @@ remove() {
   local search_hostname=""
   local search_string=""
 
-  _debug printf "remove() \${1}: %s\n" "${1:-}"
-  _debug printf "remove() \${2}: %s\n" "${2:-}"
+  _debug printf "• remove() \${1}: %s\n" "${1:-}"
+  _debug printf "• remove() \${2}: %s\n" "${2:-}"
 
   for arg in "${_COMMAND_ARGV[@]:-}"
   do
@@ -1023,9 +1023,9 @@ remove() {
     esac
   done
 
-  _debug printf "remove() \${arguments[0]}: %s\n" "${arguments[0]:-}"
-  _debug printf "remove() \${arguments[1]}: %s\n" "${arguments[1]:-}"
-  _debug printf "remove() \${arguments[2]}: %s\n" "${arguments[2]:-}"
+  _debug printf "• remove() \${arguments[0]}: %s\n" "${arguments[0]:-}"
+  _debug printf "• remove() \${arguments[1]}: %s\n" "${arguments[1]:-}"
+  _debug printf "• remove() \${arguments[2]}: %s\n" "${arguments[2]:-}"
 
   if [[ -z "${arguments[1]:-}" ]]
   then
@@ -1036,10 +1036,10 @@ remove() {
     search_ip="${arguments[1]}"
     search_hostname="${arguments[2]}"
     is_search_pair=1
-    _debug printf "remove() \${is_search_pair}: %s\n" "${is_search_pair}"
+    _debug printf "• remove() \${is_search_pair}: %s\n" "${is_search_pair}"
   else
     search_string="${arguments[1]:-}"
-    _debug printf "remove() \${search_string}: %s\n" "${search_string}"
+    _debug printf "• remove() \${search_string}: %s\n" "${search_string}"
   fi
 
   # Regular Expression Notes