Convert string to unicode literal sequence

unicode_literal_converter.tcl

package require unicode

proc to_unicode_literal {str} {
	set cs [lmap c [unicode::fromstring $str] {format \\u%04x $c}]
	join $cs ""
}

if {[namespace exists ::tk]} {
	proc copy_to_clipboard {str} {
		clipboard clear
		clipboard append $str
	}
	
	proc to_literal {} {
		global istr ostr
		set ostr [to_unicode_literal $istr]
		copy_to_clipboard $ostr
	}
	
	proc from_literal {} {
		global istr ostr
		set istr [subst $ostr]
		copy_to_clipboard $istr
	}
	
	entry .ei -textvariable istr -width 100
	button .bi -text "To Literal" -command "to_literal"
	entry .eo -textvariable ostr
	button .bo -text "From Literal" -command "from_literal"
	
	grid .ei .bi -sticky news
	grid .eo .bo -sticky news
	
	grid columnconfigure . 0 -weight 1
	grid columnconfigure . 1 -weight 0
} else {
	set str [lindex $argv 0]
	to_unicode_literal $str
}

Standalone executable is here.
https://yusuke-blog.info/wp-content/uploads/2020/03/unicode_literal_converter.zip