关于正则匹配问题

open (FI, "a.txt");
while(my $line=<FI>){
if($line=/(\d+)\n(\d+)\n(\d+)\d(\d+)\n(\d+)/){
print "$1\n";
}
这个匹配不上，求大神解答！！谢谢

while(my $line=<FI>){
if($line=~/(\d+)\n(\d+)\n(\d+)\d(\d+)\n(\d+)/){
print "$1\n";
}
加上=~这不行？为什么呢？