...in Perl. That is, in many shells, "this `is` that" does try to run the 'is' command, but Perl does not do that.

From perlop:

In particular, contrary to the expectations of shell programmers, back-quotes do NOT interpolate within double quotes, nor do single quotes impede evaluation of variables when used within double quotes.

The only characters that are special inside of double quotes are $, @, \, and your delimiter(s). For example, inside qq{}, the special characters are $, @, \, {, and }.