if (businessCall.value = "Yes_bus") {
...
Can't modify concatenation (.) or string in scalar assignment near ""Yes_bus")

That's an entirely descriptive message. You have a scalar assignment (=) when what you almost certainly want is a string equivalence test (eq). On the left hand side you have a concatenaction (.) between two barewords.

Perhaps it's time to stop typing and have a nice cup of tea and a slow, steady read through perlintro and perlsyn?