#!/usr/bin/env perl 
use strict;
use warnings;

print "Enter limit: ";
chomp( my $limit = <STDIN> );
$limit = abs($limit);

open my $in, '<', "file.hairpin" or die $!;
open my $sifted, '>', "new_file.hairpin" or die $!;

while (<$in>){
	next if /^None/;
	next if /^(\d+)/ && $1 > $limit;
	print $sifted $_;
}

close $in;
close $sifted;