The goto command wants to have a string next to it. For example:
goto "Label1"
will go to
#Label1
So, you need to pass a STRING to the script, and then pass that string to the goto command. Right now you are trying to pass whatever is in the variable loop1 to the script. Instead, you need to pass the STRING "loop1":
["loop1"] exec "script.sqs"
And in the script:
goto (_this select 0)