Regex validation for IPv4 addresses, optionally with CIDR notation

IPRegex.ps1

$IPRegex = @(
    '^(([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])\.){3}', #<-: 0. to 255. (x3)
    '([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])', #<---------: 0 to 255
    '($|/([8-9]|[1-2][0-9]|3[0-2]))$' #<-----------------------------: (optional) /8 to /32
) -join ''

$Variations = @(
    # Will match:
    '0.0.0.0',
    '10.0.0.0/8',
    '192.168.0.2/32',
    '255.255.255.255',
    # will not match:
    '256.0.0.0',
    '10.0.0.0/7',
    '192.168.0.1/33'
)

$Variations | ForEach-Object { $_ -match $IPRegex }