Mp3tag lacks case-sensitive boolean function for verifying equality of two strings. At the moment, one must resort to using regular expressions.
There's also $strcmp() function (same name as in foobar2000) but it seems to be just an alias of $eql() in spite of being case-sensitive in foobar.
According to help file syntax of two applications "should be (almost) compatible"
Please change the behavior of $eql() function or provide us with another solution.