This works for your example input, but is not general. You should be able to base the general solution on it, though. 
#!/usr/bin/perl
use warnings;
use strict;

my $level = 0;
while (<>) {
    if (m%<P_list-bull\(1\)>(.*?)</P_list-bull\(1\)%) {
        my $text = $1;
        if ($level == 0) {
            print qq{<list list-type="bullet">\n};
        } elsif ($level == 1) {
            print "</p></list-item>\n";
        } elsif ($level == 2) {
            print "</list></p></list-item>\n";
        }
        print "<list-item><p>$text";
        $level = 1;
    } elsif (m%<P_list-simple\(2\)>(.*?)</P_list-simple\(2\)>%) {
        my $text = $1;
        if ($level == 1) {
            print qq{\n<list list-type="simple">\n};
        }
        print qq{<list-item><p>$text</p></list-item>\n};
        $level = 2;
    }
}
if ($level == 1) {
    print "</p></list-item>\n</list>\n";
}

[download]
BTW, the one who created the original format probably never thought about the possibility anyone would like to use it.

In reply to Re: Multilevel tag closing by choroba
in thread Multilevel tag closing by maha

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