This:

$link->url
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... is a method call. Method calls don't interpolate in double-quoted strings. Try:

my @links = $mechObject->links();
foreach my $link (@links) {
   print $link->url;
}
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Aside: there is actually a special trick for getting method calls (in fact, arbitrary code) to interpolate in strings though:

print "Here it is: @{[ $link->url ]}!\n"
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