Bug? Strange behavior Regex

fileStr = "/book/assets/img/logo.png"
            Dim dirFound As Boolean = Regex.IsMatch($"(.*)[\/\\]"$,fileStr)
            Log(dirFound)

            fileStr = "/book/assets/img/logo.png"
            Dim dirFound As Boolean = Regex.IsMatch2($"(.*)[\/\\]"$,Regex.CASE_INSENSITIVE,fileStr)
            Log(dirFound)

Dim m As Matcher = Regex.Matcher2('pattern', 'options', 'text')
Do While m.Find
 Log("Match: " & m.Match)
 For g = 1 To m.GroupCount
  Log("Group #" & g & ": " & m.Group(g))
 Next
Loop

Dim Pattern As String = "(.*)[\/\\]"
Dim Text As String = "/book/assets/img/logo.png"

Dim m As Matcher = Regex.Matcher(Pattern, Text)
If m.Find Then
    Log("Match: " & m.Match)
Else
    Log("Nice try, no cigar.")    'or whatever is to be done if no match found :-)
End If