/usr/share/konwert/devel/fixtrsutf8 is in konwert-dev 1.8-11.2build2.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 | #!/usr/bin/perl
sub popraw ($$)
{
	$_ = $_[1];
	/([^\\]|\\[^[])*\\\[/g or return "$_[0]$_\n";
	my $przed = $_[0] . substr ($_, 0, pos() - 2);
	$_ = substr ($_, pos());
	my %przedrostki = ();
	until (/^\\\]/g)
	{
		if (/^()([^\\\200-\377]|\\.)/g
		|| /^([\300-\337])([\200-\277])/g
		|| /^([\340-\357][\200-\277])([\200-\277])/g)
		{
			$przedrostki{$1} .= $2;
			$_ = substr ($_, pos());
		}
		else {die "Syntax error or bad UTF-8 at line $.\n"}
	}
	my $reszta = substr ($_, pos());
	return map
	{
		popraw
		(
			"$przed$_" .
			(
				length $przedrostki{$_} == 1 ? $przedrostki{$_}
				: "\\\[$przedrostki{$_}\\\]"
			),
				$reszta
		)
	}
		keys %przedrostki
}
while (<>)
{
	chomp;
	print /^#/ ? "$_\n" : popraw ("", $_);
}
 |