use strict;
use warnings;

while (1) {
    print "Customer abbreviation:         ";
    my $cust = <STDIN>;
    print "\n";
    chomp ($cust);
    
    last if $cust =~ /\w{3,4}/;
    
    print <<EOT;
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!                                        !!!
!!! ABBREVIATION MUST BE 3 OR 4 CHARACTERS !!!
!!!                                        !!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

EOT
}