/* No escape */
#define MESSAGE1 "${var1}"

/* Single escape means no replace */
#define MESSAGE2 "\${var1}"

/* Replace pairs of escapes before '@' or '\@' with escape characters
 * (note we have to double number of pairs due to C string escaping)
 */
#define MESSAGE3 "\\\\${var1}"

/* Pairs of escapes and then single escape to avoid replace */
#define MESSAGE4 "\\\\\${var1}"

/* Check escape character outside variables */
#define MESSAGE5 "\\ ${ \${ \\\\${ \\\\\${"