Here's my guess at something like what you want. Instead of printing @match and @nomatch at the end, just write their contents to the proper files, and change the input to read from your input file. 

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11109150
use warnings;

my $x = 9;

my %uniques;
my @match;
my @nomatch;

while( <DATA> )
  {
  print;
  for my $element ( split )
    {
    if( keys %uniques < $x )
      {
      $uniques{ $element }++;
      }
    else
      {
      if( $uniques{ $element } )
        {
        push @match, $element;
        }
      else
        {
        push @nomatch, $element;
        }
      }
    }
  }

print "\nMATCH:\n@match\n\nNOMATCH:\n@nomatch\n";

__DATA__
1 2 6 4 5
6 7 8 9 10
1 2 11 12 13
6 14 15 16 17

[download]

Outputs: 

1 2 6 4 5
6 7 8 9 10
1 2 11 12 13
6 14 15 16 17

MATCH:
1 2 6

NOMATCH:
11 12 13 14 15 16 17

[download]

In reply to Re^3: Reversing the action of the while loop by tybalt89
in thread Reversing the action of the while loop by Scotmonk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.