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

my %fhs;

my $molecule = "1kc4";

open my $FILE, '<', 'input_file' or die $!;
while (<$FILE>) {

  chomp;
  my @columns = unpack('a8 a8 a8 a6');
  #print join(" ",map {$_} @columns), "\n";
  #print "@columns[3] \n";
    
  foreach (@columns[$#columns]) {
 
    my $abs = abs( $columns[ $#columns ] );

    open $fhs{ $abs }, '>', "${molecule}_cluster_" . $abs or die $! unless exists $fhs{ $abs };
    my $file = $fhs{ $abs };
         
      my $ID = $_;
      my $IDform = sprintf ("%4s", $ID);
     
      my $currentline = $.;
      my $currentlineform = sprintf ("%7s", $currentline);##

      my @selection = (@columns[0..$#columns-1]);
      my $layout = "%10s"x(@selection) . "\n";

      printf $file $IDform . $currentlineform . $layout, @selection;
  }
}
##</code><code>##

The output filenames are correct and one of them looks like this:

    8    109   -42.129   -57.475    94.651
    8    110   -45.520   -62.056    90.318
    8    111   -49.196   -63.045    92.577
    8    112   -46.086   -71.753    88.267
   -8    113   -48.146   -76.799    77.638
    8    114   -41.865   -62.567    86.437