WWW::Mechanize should take care of hidden fields automatically, so you could delete these lines:

for ($output =~ /name=\"DV_DATA\" type=\"hidden\" VALUE=\"(.*?)\">/smi
+){
    
    $dv_data = $1;
    
}
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and this line:

    DV_DATA => $dv_data
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This line is wrong:

$webpage =~ s/\'\//\"$base_address\//smig;
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because of the quote mismatch. (Also, only the g flag is actually needed on this statement.)

You might want something like:

  $webpage =~ s!(=['"])/!$1$base_address/!g;
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