$/=undef;open+A,"+<".shift;$_=<A>;s/(<[^<>]+>)/\n$1\n/g;seek
A,0,0;$r='(?:[\t\n\s]+)?';for(split/$r\n$r/){$t--if/<\/[^bcop
]/i;$_="\t"x$t.$_;$t++if/<[^\/bci-p!]/i;print A"$_\n"}close(A)