foreachLine substitution code reference

This example in the Mail::Message::Body foreachLine docs
doesn't work for me.

        $content->foreachLine( sub {(my $x=$_) =~ s/a/A/} );

This does:
        $content->foreachLine( sub {(my $x=$_) =~ s/a/A/; return $x} );

The other examples work.

I wonder if it is a problem of arrays being returned in scalar
context, because the output of the first type is a sequence of
digits, typically 1, like 1111111.

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