请教！向文件头部写入不同于已有内容的行和

请教！向文件头部写入不同于已有内容的行和
请教！向文件头部写入不同于已有内容的行和向文件尾部写入不同于已有内容的行
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#向文件头部写入不同于已有内容的行
open F , "+< n.txt";
chomp (my @lines1 = <F>);
my $newline1 = 5;
my $re1 = 0;
for (@lines1) {
$re1 = 1 if $_ eq $newline1;
}
unshift @lines1, $newline1 unless $re1;
truncate F, 0;
seek F , 0 ,0;
for (@lines1) {
print F $_,"\n";
}
close F;
+++++++++++++++++++++

#向文件尾部写入不同于已有内容的行
open F , "+>> n.txt";
seek F, 0,0;
chomp (my @lines = <F>);
my $newline = 5;
my $re = 0;
for (@lines) {
$re = 1 if $_ eq $newline;
print "\$_:|$_|\$newline:|$_|";
}

print F $newline,"\n" unless $re;
close F;

你想问啥？