Segment matcher inappropriately matches on substring

In ScalaFormHelpers.md:

@[form-myfield](code/scalaguide/forms/scalaformhelper/views/user.scala.html)

will match inappropriately -- in user.scala.html, the link will include the output from

@* #form-myfield-helper*@
@helper.inputText(myForm("username"))
@* #form-myfield-helper*@

Because it looks for "form-myfield" instead of the entire label.