In theory, if you don't need interpolation, using single quotes could compile a tiny bit faster, but a) perl compiles blazingly fast compared to most languages, and b) the time needed to analyze a quoted string is probably dwarfed by the time needed to load the perl interpreter and the rest of the code. Don't worry about it.

Also, using double-quotes makes it slightly easier to insert variables into the string later, which is why i generally prefer to use double-quoted strings for all literals that don't contain a lot of "meta" characters.