in reply to Re^2: Problem using value of variable in a regular expression
in thread Problem using value of variable in a regular expression

It's not undesirable at all. In double quotes, the backslash is indicates the start of an escape allowing "\n" to mean newline, "\"" to mean a double quote, etc. Double quotes are documented in perlop.

You're just using the wrong tool.

$failmsg = qr/\*E/;