Not really a proper Perl solution, but I couldn't find out how to make the low level routines in Net::SSLeay work (the documentation states that the certificate verification code isn't well tested). Anyway, here's an Inline C bit of code that works on Debian Stretch:

use strict;
use warnings;

use Inline Config =>
           force_build => 0,
           clean_after_build => 1;
use Inline C => 'DATA';
use Inline C => Config =>
                DIRECTORY => "/tmp" =>
                enable => 'UNTAINT' =>
                inc => '-I/usr/include' =>
                libs => ' -lssl -lcrypto ';

my $CAfile = "cacert.pem";
my $Cert = "good.crt";
my $Cert2 = "selfsigned.crt";
print "cert1 = " . verify_cert($CAfile, $Cert) . "\n";
print "cert2 = " . verify_cert($CAfile, $Cert2) . "\n";

__DATA__
__C__

#include <openssl/bio.h>
#include <openssl/err.h>
#include <openssl/pem.h>
#include <openssl/x509.h>
#include <openssl/x509_vfy.h>

char *verify_cert(char *ca_bundlestr, char *cert_filestr) {


  BIO              *certbio = NULL;
  BIO               *outbio = NULL;
  X509          *error_cert = NULL;
  X509                *cert = NULL;
  X509_NAME    *certsubject = NULL;
  X509_STORE         *store = NULL;
  X509_STORE_CTX  *vrfy_ctx = NULL;

  int ret;
  char *retmsg;

  OpenSSL_add_all_algorithms();
  ERR_load_BIO_strings();
  ERR_load_crypto_strings();

  certbio = BIO_new(BIO_s_file());

  if (!(store=X509_STORE_new())) {
     size_t needed = snprintf(NULL, 0, "Error creating X509_STORE_CTX 
+object") + 1;
     retmsg = malloc(needed);
     snprintf(retmsg, needed, "Error creating X509_STORE_CTX object");
     goto done;
  }

  vrfy_ctx = X509_STORE_CTX_new();

  ret = BIO_read_filename(certbio, cert_filestr);
  if (! (cert = PEM_read_bio_X509(certbio, NULL, 0, NULL))) {
     size_t needed = snprintf(NULL, 0, "Error loading cert into memory
+") + 1;
     retmsg = malloc(needed);
     snprintf(retmsg, needed, "Error loading cert into memory");
     goto done;
  }

  ret = X509_STORE_load_locations(store, ca_bundlestr, NULL);
  if (ret != 1) {
     size_t needed = snprintf(NULL, 0, "Error loading CA cert or chain
+ file") + 1;
     retmsg = malloc(needed);
     snprintf(retmsg, needed, "Error loading CA cert or chain file");
     goto done;
  }
  X509_STORE_CTX_init(vrfy_ctx, store, cert, NULL);

  ret = X509_verify_cert(vrfy_ctx);

  if( ret == 0 ) {
     size_t needed = snprintf(NULL, 0, "Error %s", X509_verify_cert_er
+ror_string(X509_STORE_CTX_get_error (vrfy_ctx))) + 1;
     retmsg = malloc(needed);
     snprintf(retmsg, needed, "Error %s", X509_verify_cert_error_strin
+g(X509_STORE_CTX_get_error (vrfy_ctx)));
  } else {
     size_t needed = snprintf(NULL, 0, "OK") + 1;
     retmsg = malloc(needed);
     snprintf(retmsg, needed, "OK");
  }
done:
  X509_STORE_CTX_free(vrfy_ctx);
  X509_STORE_free(store);
  X509_free(cert);
  BIO_free_all(certbio);
  return( retmsg );
}
[download]

running it:

$ perl verify_certs.pl
cert1 = OK
cert2 = Error self signed certificate
[download]

(code is based on this source: original C code )

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