Imports System
Imports System.Text.RegularExpressions
 
Public Class Test
	Public Shared Sub Main() 
		Dim i As Integer
		Dim pattern As String = "(?<=\()[a-z]+(?=\((?:\((\d+)\))?(?:\((\d+)\))?\))"
		Dim text As String = "(abc())(def((123)(456))(klm((123))"
		Dim matches As MatchCollection = System.Text.RegularExpressions.Regex.Matches(text, pattern)
		For Each m As Match In matches
			i = 0
		    For Each g As Group in m.Groups
		    	If i = 0 Then
		    		Console.WriteLine("Match: " & g.Value)
		    	ElseIf i > 0 and g.Value <> "" Then
			        Console.WriteLine("Group " & i & ": " & g.Value)
			    End If
			    i = i + 1
		    Next
		Next
	End Sub
End Class

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