Regular expression validation start two fixed character

Question

Required Regex Validation Start two Fixed character and then after First point required alphanumeric characters and second point required Numeric fixed Character.

Example:

1. if character start with PB then allow 25 character

- Length : additional 25 numbers. - Example : PB12345Ab8901234567890123mM If “PB” then 25 alphanumeric characters. PB+25numbers

2. if character start with CC then allow 14 character

- Length : additional 14 numbers. - Example : CC012345678901234 If “CC” then 14 numbers. CC+14numbers

 

(?:PB[\da-zA-Z]{25}|CC\d{14})$ i need in this expression add one more condition if string not start with PB or CC then it's allow 0 to 100 character.