check xml tag error

xml_checker.rb

# encoding: utf-8

def find_tag(str)
    if str =~ /<\/(.*?)>/mu
        return {is_begin: false, tag: $~.captures.first}
    end
    if str =~ /<(.*?)( |>)/mu
        return {is_begin: true, tag: $~.captures.first}
    end
end

str = File.read(File.expand_path('~/Google Drive/temp//LibraryMessages_en.xlf.xml'), :encoding => 'utf-8')
pattern = /(<.*?>)/mu
matches = str.to_enum(:scan, pattern).map { Regexp.last_match }

begin_tags = []

matches.each do |match|
    if match.to_s =~ /<(\?|!).*?>/mu or match.to_s =~ /<.*?\/>/mu
        next
    end
    tag = find_tag(match.to_s)
    if tag
        # puts match.to_s
        # puts "tag is " + tag[1]

        if tag[:is_begin] # begin tag
            begin_tags << {match: match, tag: tag[:tag]}
            # puts 'push begin tag: ' + tag[:tag]
        else # end tag
            begin_tag = begin_tags.pop
            if begin_tag[:tag] == tag[:tag]
                # puts '  pop begin tag: ' + tag[:tag]
                next
            else
                puts '============================================'
                puts 'error find at line: #' + (str[0..begin_tag[:match].begin(0)].count("\n")+1).to_s
                puts 'begin tag is: ' + begin_tag[:tag]
                puts 'begin match is: ' + str[begin_tag[:match].begin(0), 100]
                puts 'current tag is: ' + tag[:tag]
                puts 'current match is: ' + str[match.begin(0), 100]
                puts '============================================'
                break;
            end
        end
    end
end

puts 'success'