VBScript のプロパティ、Pattern プロパティ x|y

Set r = New RegExp

str = "abc"
r.Pattern = "a|bbc"
Set Matches = r.Execute(str)
MsgBox Matches(0) ' a

r.Pattern = "(a|b)bc"
Set Matches = r.Execute(str)
MsgBox Matches(0) ' abc

r.Pattern = "(abc|b)"
Set Matches = r.Execute(str)
MsgBox Matches(0) ' abc