my @tests = (               
    'First case',           
    '123456789second & third case',
);                          
                            
for my $t (@tests) {        
    print "\nchecking '$t'\n";                                                  
    if ($t=~/(\d{4,}?)(.*)/)   { print "A: $1, $2\n"; }
    if ($t=~/(\d{4,}?)(.*?)$/) { print "B: $1, $2\n"; }
}