use strict;
use warnings;
use IPC::Open3;

my ($msg_out,$err_out);

eval { open3(undef, *OUT, *ERR, @ARGV) };

if ($@) {
    $msg_out = '';
    $err_out = "invalid command '$ARGV[0]'";
}
else {
    $msg_out = do {local $/;<OUT>};
    $err_out = do {local $/;<ERR>};
}

print "STDOUT: $msg_out\n";
print "STDERR: $err_out\n";