#!/usr/bin/perl

###############
## Libraries ##
###############
use strict;
use warnings;
use feature qw{ say };
use Crypt::OpenSSL::RSA;
use Data::Dumper;
use Function::Parameters;
use IO::File;


##################
## User-defined ##
##################
my $pubfile  = "./key.pub";
my $privfile = "./key.priv";
my $keysize  = 1024;
my $message  = 'A quick brown fox jumps over the lazy dog.';


##################
## Main Program ##
##################
create_rsa_keys();                          # Create keys, save to disk
my $pub  = pubkey_from_file($pubfile);      # Construct public key from disk
my $priv = privkey_from_file($privfile);    # Construct private key from disk
my $enc  = encode($pub,  $message);         # Encode the message
my $dec  = decode($priv, $message);         # Decode the message
say "Result '$dec'";                        # Results (if error is fixed!)


#################
## Subroutines ##
#################
fun create_rsa_keys() {
    # Generate the public & private key text, and save to disk
    my $genkeys  = Crypt::OpenSSL::RSA->generate_key($keysize);
    my $pubtext  = $genkeys->get_public_key_string();
    my $privtext = $genkeys->get_private_key_string();
    key_to_file('Public key',  $pubfile,  $pubtext);
    key_to_file('Private key', $privfile, $privtext);
}


fun key_to_file($label, $path, $text) {
    my $fh = IO::File->new;
    open($fh, ">", $path) or die "Failed to write $label to '$path' ($!)\n";
    print $fh $text;
    close($fh);
}


fun pubkey_from_file($path) {
    my $text = file_to_string('Public key', $path);
    my $pubkey = "";
    eval { $pubkey = Crypt::OpenSSL::RSA->new_public_key($text) };
    $@ and die "Error in string_to_public_key ($@)\n";
    return $pubkey;
}


fun privkey_from_file($path) {
    my $text    = file_to_string('Private key', $path);
    my $privkey = "";
    eval { $privkey = Crypt::OpenSSL::RSA->new_private_key($text) };
    $@ and die "Error in string_to_private_key ($@)\n";
    return $privkey;
}


fun file_to_string($label, $path) {
    local $/ = undef;
    my $fh   = IO::File->new;
    open($fh, "<", $path) or die "Failed to read $label '$path' ($!)";
    my $text = <$fh>;
    close($fh);
    return $text;
}


fun encode($pubkey, $plain) {
    my $encode = "";
    eval { $encode = $pubkey->encrypt($plain) };
    $@ and die "Failed to encode plaintext ($@)\n";
    return $encode;
}


fun decode($privkey, $encode) {
    my $decode = "";
    eval { $decode = $priv->decrypt($encode) };
    $@ and die "Failed to decode encrypted text ($@)\n";
    return $decode;
}


__END__
The public key file looks okay:

-----BEGIN RSA PUBLIC KEY-----
MIGJAoGBAMjDisZYXREArFdv5VrP/U1tzh7NShzQgVBN4Kb+2xNwkIhPZd3hv98f
w3p/9IigAFhUBnXnNSnOsvZJ79/M8WZ5fOoQQzre8jyw84Z2H/nQsLZCkkN4n52H
Byg+K5dSNCh3K0UdTN/Li6nbS19OTweGz3X+oKNPb+oZtwPQ5C+TAgMBAAE=
-----END RSA PUBLIC KEY-----

As does the private key file:

-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----