汉字的割接

#!/usr/bin/perl
use Encode;
while(<>){
        chomp;
        $subj=$_;
        $a=length($_);
        if($a >15){
        #$b=$;
        $aa =substr ($_,0,4);
        }

        $subj=decode('gb2312',$subj);
        $length=length($subj);
####################################################
         if($length<227){
                $subj=substr($subj,0,4);
                      }
        $subj=encode("gb2312",$subj);
        print "$b$_|$aa length $a|subject $subj\n";
        }