Ok after some testing it appears that what it is looking for is words containing 4 Chars.
Here is a small sample that rewrites most of the code used, using the above link as a guide and using a rich text box for input and a standard texbox for output here is what I ended up with.
Input is this.
this is a tesssssst for to mannnnnnny leters tttt AbCd
Output is this.
this
tttt
AbCd
Private Sub btnTest_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnTest.Click
Try
Dim strbldr As New StringBuilder
Dim regtext As String
If tbInput.Text = Nothing Then
MsgBox("Nothing was entered")
Exit Sub
Else
regtext = tbInput.Text
End If
Dim pattern As String = ("\b\w{4}\b")
Dim rgx As New Regex(pattern)
For Each M As Match In rgx.Matches(regtext)
strbldr.AppendLine(M.ToString)
Next M
tbOutput.Text = strbldr.ToString
Catch ex As Exception
MsgBox(ex.Message)
End Try
End Sub