use IO::Socket::SSL;
my $cl = IO::Socket::SSL->new(
    PeerAddr => "ip:port", 
    SSL_verify_mode => 0
);
print $cl->get_fingerprint."\n"; # sha256$b64d26746ca1cd5403....

##</code><code>##

my $ua = LWP::UserAgent->new...
$ua->ssl_opts(SSL_fingerprint => 'sha256$b64...');