重复内容删除的小脚本

加入说序列式这样的

1 2
1 2
2 1
1 3
1 4
1 5
4 1


我们得出的结果如下：
1 3
1 5
2 1
4 1


程序如下：
use strict;
use warnings;

my $filename;
my %hash;
my @information;
my $key1;
my $key2;

print "please put in the file like this f:\\\\perl\\\\data.txt\n";
chomp($filename=<STDIN>);
open(IN,"$filename")||die("can not open");
while(<IN>)
{
chomp;
@information=split/\s+/,$_;
if(exists $hash{$information[0]}{$information[1]})
{
next;
}
else
{
$hash{$information[0]}{$information[1]}='A';
}
}
close IN;

open(IN,"$filename")||die("can not open");
while(<IN>)
{
@information=split/\s+/,$_;
if(exists $hash{$information[1]}{$information[0]})
{
delete $hash{$information[0]}{$information[1]}
}
else
{
next;
}
}
close IN;

open(OUT,">f:\\A_B_result.txt")||die("can not open");
foreach $key1 (sort{$a<=>$b} keys %hash)
{
foreach $key2 (sort{$a<=>$b} keys %{$hash{$key1}})
{
print OUT "$key1 $key2\n";
}
}
close OUT;