!/usr/bin/perl -w
 use strict;
 
 #print "please input a string\n";
 #my $line = STDIN>;
 #print $line;
 
 #wirte a file
 open(FH, ">aa.txt") or die $!; 
 print FH "hello\n";#向文件写入内容
 print FH "OK\n";
 
 close(FH);
 
 #open a file
 open(FH, "aa.txt") or die $!;
 my @f = FH>;#将文件内容读出
 print @f;
 
 close(FH);