Solution of Registration Plates

This problem admits some very short solutions, based on regular expressions:

Sergiu Pușcaș - Python 3

    1 #!/usr/bin/python3
    2 import re
    3 
    4 for _ in range(int(input())):
    5     s = input()
    6     print("Correct!" if re.match("[A-Z]{2}\s[0-9]{2}\s[A-Z]{3}", s) or \
    7                         re.match("B\s[0-9]{2,3}\s[A-Z]{3}", s) else "Incorrect!")

Petru Trîmbițaș - Perl

    1 use v5.16;
    2 use warnings;
    3 
    4 my $n = <>;
    5 chomp $n;
    6 for (1..$n) {
    7     my $line = <>;
    8     chomp $line;
    9     if($line =~ /^(([A-Z][A-Z]\ [0-9]{2})|(B\ [0-9]{2,3}))\ [A-Z]{3}$/) {
   10         say "Correct!";
   11     } else {
   12         say "Incorrect!";
   13     }
   14 }

Marius Gavrilescu - Perl

    1 #!/usr/bin/perl
    2 use v5.14;
    3 use warnings;
    4 <>;
    5 say /^([A-Z][A-Z] \d\d|B \d{2,3}) [A-Z]{3}$/ ? 'Correct!' : 'Incorrect!' while <>;