#!/usr/bin/perl
            
use Switch;
        
$/ = \1;
         
$state = 'DOCUMENT';
            
while (<>) {
    switch ($state) {
        case 'DOCUMENT' {
            $state = 'TAG' if /\x3C/;
        }
        case 'TAG' {
            $state = /\x21/ ? 'DECLARATION' : 'ELEMENT';
        }
        case 'ELEMENT' {
            $state = 'SINGLE_QUOTE'   if /\x27/;
            $state = 'DOUBLE_QUOTE'   if /\x22/;
            $state = 'DOCUMENT_TO_BE' if /\x3E/;
        }
        case 'SINGLE_QUOTE' {
            $state = 'ELEMENT' if /\x27/;
        }
        case 'DOUBLE_QUOTE' {
            $state = 'ELEMENT' if /\x22/;
        }
        case 'DECLARATION' {
            die "Parse error" unless /\x2D/;
            $state = 'COMMENT_START';
        }
        case 'COMMENT_START' {
            die "Parse error" unless /\x2D/;
            $state = 'COMMENT';
        }  
        case 'COMMENT' {
            $state = 'COMMENT_END' if /\x2D/;
        }
        case 'COMMENT_END' {
            $state = /\x2D/ ? 'COMMENT_TRAIL' : 'COMMENT';
        }   
        case 'COMMENT_TRAIL' {
            die "Parse error"     unless /[\x22\x3E\s]/;
            $state = 'COMMENT_START'  if /\x22/;
            $state = 'DOCUMENT_TO_BE' if /\x3E/;
        }
    }
    print $state eq 'DOCUMENT' ? $_ : " ";
    $state = 'DOCUMENT' if $state eq 'DOCUMENT_TO_BE'
}
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