#!/usr/bin/perl

use strict;
use warnings;

my @files = grep { $_ !~ /^~/ } (<*.txt>);
my @matches;

foreach my $file (@files) {
    open (my $fh, '<', $file) or die $!;
    /(NR \d{7})/g and push @matches, $1 while (<$fh>);
    close $fh or die $!;
}

print "@matches\n";