With the pointer to the RSA module the following code does the trick for me :) 
use Crypt::OpenSSL::RSA;
use Crypt::OpenSSL::X509;
use File::Slurp;
use MIME::Base64;

my $x509 = Crypt::OpenSSL::X509->new_from_file('cert.pem');
my $pubkey = Crypt::OpenSSL::RSA->new_public_key($x509->pubkey());
$pubkey->use_sha256_hash();

my $sigbase64 = read_file('signature.txt' , binmode => ':raw' );
my $data = read_file('data.txt' , binmode => ':raw' );

my $signature = decode_base64($sigbase64);
my $valid = $pubkey->verify($data, $signature);

print "Is valid: $valid\n";

[download]
this is equivalent to the Python code posted in the original question.

In reply to Re: Verify signed data by rjschwei
in thread Verify signed data by rjschwei

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