Perhaps it'd be nice if WWW::Mechanize::Link had '""' overloaded to return the URL, when stringified. It would produce more "intuitive" results for normal use.

You can currently produce that result by adding this to your code:

use WWW::Mechanize;
BEGIN {
    package WWW::Mechanize::Link;
    use overload '""' => \&url_abs;
}
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OTOH it wouldn't do much good in your case, as you're trying to generate a HTML page of links. A simple, plain text, list of links then isn't much good.