# subroutine name: safe_tag
# HTML-encodes string (prepare data for HTML output)
# Replaces:
# & -> &
# < -> &lt;
# > -> &gt;
# " -> &quot;
# \x0D -> remove
sub safe_tag {
	my ($input) = @_;
	$input =~ s/&/&amp;/sg;
	$input =~ s/\</&lt;/sg;
	$input =~ s/\>/&gt;/sg;
	$input =~ s/\"/&quot;/sg;
	$input =~ s/\x0D//sg;
	$input=~s/([\x01-\x08\x0B-\x1F])/"&#".ord($1).";"/esg;
	$input;
}