in reply to
fourth digit should not match digit "2"
See the answers you (or your cohort) got to Regex for last digit should not be "2" and adapt them. Maybe consider reading your course material, and/or perlre or perlretut.
A Programming Language, 1962
Programming the 1900 series in COBOL, 1974
Algorithms + Data Structures = Programs, 1976
The C Programming Language, 1978
System V - Interface definition, 1986
Z80 Assembly Language Programming, 1979
TheSOURCE User's Manual, 1979
The C Primer, 1983
Interactive Fortran 77, A Hands on Approach, 1984
Perl.1 man page, 1991
Results (354 votes),