Another simple option is to pack the string into UUE. As with some of the other answers, this provides extremely limited security (bordering on none at all), it merely obscures the text. It doesn't seem to add too much length of the messages I tested. Example:

my $msg = pack "u", "Secret message that is not so secret";
print "Obscured: $msg";
print "Plain: ", unpack("u", $msg), "\n";
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