Well hopefully the implementation does not change. Yes I know famous last words. But lvalue is an experimental feature. That has its problems too.
<update>It just occured to me that ...

s/foo/bar/g;
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... could take place in the class defintion. That wouldn't violate encapsulation would it? All one would have to do is add a method to the class. Something like ...

sub s {
        my ( $obj, $pat, $sub ) = @_;
        $obj->{'content'} =~ s/$pat/$sub/g;
}
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I wonder if it would be possible to use overload ... you know something like ...

use overload
      "s" => \&s;
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