Yes, you found the correct way to do what you were trying to do. The documentation in perlop may not be particularly clear, but the "*" next to "yes" in the "Interpolates" column is explained as "unless the delimiter is ''". So you can use single quotes to prevent interpolation with qx, m//, qr, s///, and here-docs.
XML::Simpler does not require XML::Parser or a SAX parser. It does require File::Slurp.
-- grantm, perldoc XML::Simpler