用perl提取字符串子集的代码

#!/usr/bin/perl

use warnings;
use strict;

my @file1;
my $x,;

open(INFILE1, "E:/chr1.txt");
open(INFILE2, "E:/SNP_position.txt");
open OUT1,'+>E:/60_10000_seq.txt';

chomp(my @contents = <INFILE1>);
my $all_text = join('', @contents);

foreach $x(<INFILE2>){
        chomp $x;

        my $subseq = substr($all_text, $x-30, 60);
    print OUT1 "$xt$subseqn";
  }
exit;