From looking at the documentation ( Can't test this as am currently away from my windows box ).
Looks like you need to do something like this:

my @links = $ie->getAllLinks();
$links[0]->linkUrl();
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linkUrl is a method of the 'link obj' not 'Win32::IEAutomation as stated: "Methods supported for link object". The object returned by 'getAllLinks' is 'Win32::IEAutomation::Element' which is the link obj. @links is therefore an array of objects 'hence the hash reference (How perl OO works see link below)'.
You can peek inside what a ref variable is by using Data::Dumper
Like so:

use Data::Dumper;
print Dumper( $link[0] );
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For more information have a look at at some of the perldoc tutorial on obj's perltoot understanding the insides really aids in the understanding of using them.
Hope that helps
- John
Ps. use < code > tag in future when listing code in a post.