You could possibly solve it by supporting single quotes for value containment:

    curl --jp "x='$var'"

Gives:

    curl --jp "x='foo,y=bar'"

Assuming that is what you meant. Isn’t this normally how these things are handled in unix shells? That and escaping which probably doesn’t apply here.

I don’t know what the best way to implement this would be, but the current proposal looks so weird for me that I’m either completely missing something or it’s wildly unnecessary.

If you do something like single quotes then you can no longer use the shell's abilities to properly pass in escaped values like this:

  bash$ foo=this\"test\"
  bash$ echo "value of \$foo is: $foo"
  value of $foo is: this"test"

If we're throwing away the ability to let the shell handle escaping properly then there's really no point to --jq at all versus just manually attempting to cobble together JSON directly