if {![exists -proc ::json::escape]} {

	# Initialise a map from control characters to JSON escaped characters.
	# Initially all non-null control characters to \u00xx sequences.
	for {set i 1} {$i < 32} {incr i} {
		set ::json::escape_map([format %c $i]) \\u[format %04x $i]
	}

	# Then overwrite certain well known control characters with shorter
	# versions.
	set ::json::escape_map([format %c 8]) \\b; # backspace
	set ::json::escape_map([format %c 9]) \\t; # tab
	set ::json::escape_map([format %c 10]) \\n; # lf
	set ::json::escape_map([format %c 12]) \\f; # ff
	set ::json::escape_map([format %c 13]) \\r; # cr
	# Other special sequences
	set ::json::escape_map(\") {\"}
	set ::json::escape_map(\\) {\\}
	set ::json::escape_map(/)  {\/}

	proc ::json::escape {in} {
		return [string map $::json::escape_map $in]
	}

	alias jescape ::json::escape
}