If you can't rely on having only one tag per line, then I'd probably go with something like this: 

my @list= "external";
s[(?<=<)([^>]+)(?=>))]{
    my $tag= $1;
    if(  $tag eq "item"  ) {
        "$list[-1]-$tag";
    } else {
        if(  $tag eq "end-list"  ) {
            pop @list   if  1 < @list;
        } elsif(  $tag =~ /(\w+)-list/  ) {
            push @list, $1;
        }
        $tag;
    }
}ge;

[download]

Note that you can still read the input line-by-line to avoid having to fit some entire huge file into memory at once (or set local $/= ">";); just put my first line outside of your read/write loop and the s///ge inside the read/write loop.

- tye        

In reply to Re: Nested list items (s///ge) by tye
in thread Nested list items by Anonymous Monk

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