"...Is there something I'm missing? .."

Previous comments are true, when you are on UNIX systems, but reverse is the case on Win systems.
This example perl -e "print $ARGV[1];" ONE- TWO- ## prints TWO- works as expected on Win system. But with single-quotes, you get this error message: Can't find string terminator "'" anywhere before EOF at -e line 1.

In fact, perlrun has this to say: ...On some systems, you may have to change single-quotes to double ones, which you must not do on Unix or Plan 9 systems...