#!/lang/perl
# NOTE html input to this program should have been through `htmlsplit' and `html2xhtml' already!
# tags must be on lines of their own, etc.
$tab = $ARGV[0];
if ($tab != 0) { $tab = " " x $tab; }
if (!$tab) { $tab = "\t"; }
while (defined ($_ = <STDIN>)) {
	if (m,^</,) { $i--; }
	print $tab x $i, $_;
	if (m,^<[^/!], && m,[^/]>$,) { $i++; }
}