imacros - going back to TAB T=1

Question

Why doesn't this code work in Firefox? Why doesn't it execute the last command and go back to Tab 1 in the end?

iimPlay ("CODE: TAB T=1");
iimPlay ("CODE: TAB OPEN");
iimPlay ("CODE: TAB T=2");
iimPlay ("CODE: URL GOTO=https://vk.com");
iimPlay ("CODE: TAB T=1");

I expected that Tab 1 will open again.