use Net::Patricia;

  my $pt = new Net::Patricia;
my @ar = ("82.94.229.0/24", "81.52.140.0/24");
 $pt->add_string(@ar, "@ar");

my $dude = $pt->match_string('81.52.140.209');

print "$dude\n";
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->add_string does not take an array as its first parameter, and it is documented to only take one or two parameters overall. As your array @ar contains two elements, your call is equivalent to

 my @ar = ("82.94.229.0/24", "81.52.140.0/24");
 $pt->add_string("82.94.229.0/24", "81.52.140.0/24", "82.94.229.0/24 8
+1.52.140.0/24");
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I don't know what this means to Net::Patricia, but you will either need to read the documentation for Net::Patricia closer or learn more about Perl and how it flattens lists.

Your use of add_string looks wrong according to the documentation which gives the function interface as:

  $pt->add_string(key_string[,user_data]);
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Note that the [,user_data] means you can provide optional user data along with the string. However you call the function passing an array containing two strings then follow up with a third string formed by interpolating the same array.

I haven't the module installed so I won't offer any code as I can't test it. The documentation seems pretty clear to me so I suggest you re-read the docs and take a careful look at the example code. Note that add_string returns undef on failure so you can easily check to see that the module isn't grumpy with the way you are using it.

True laziness is hard work

foreach my $pat (@ar) {
  $pt->add_string($pat);
}
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