Y2K Again ??

Good evening everybody,
I have been working on a small database project and have come across the 
need to move some data from table A to table B, the year format in table 
A is \d{2}\D{8} and in table B \d{4}\D{8}

Since the records in table A range from 1970 - 2004.  I want to be able 
look at the date, and determine if it is a 2000 or 1900 date and make 
the appropiate date change.

So here is my sollution (long):
#Pull the value out of the field
#For this example I don't care about the rest of FieldA I just want the 
1st 2 digits,
#but I need to preserve FieldA for later use in the program.

($Yr = $FieldA) =~ s/^(\d{2}).*/$1/;
if($Yr > 20){
    $Yr = "19$Yr";
}else{
    $Yr = "20$Yr";
}

#Concat year to FieldB

I guess I am looking for a way to combine a substitution with the if 
statement but haven't come up with a working solution.

Anyways, I am looking forward to see what the outcome is.

Brian