Read up on the evaluate function. It does not do what you think.
PatternCount and Exact are two string compare tools.
I highly recommend learning all of the text and value list functions as they are the bread and butter of FM.
And you should see how the comparison operators work with strings
FileMaker training series is also a great place to start
In addition to that, I can compare two strings in expressions like these:
"string a" = "String b"
"string a" > "string b"
and so forth. And in each of the places where you see quoted text in those examples, I could also use a variable or a reference to a text field to compare strings in the same fashion.