No. It is actually string concatenation. What you actually get is that an original string is broken into several parts. That are concatenated as following:
-d'{....' + ' + '....}'
@<1722061389024989184:profile|ResponsiveKoala38> Got following error. Sorry for a screenshot, I can't copy text from web terminal I am using right now.
@<1722061389024989184:profile|ResponsiveKoala38> My bad, I was indeed using double quotes. I fixed it and now script is working. I'll wait for results