I have a data that looks like this:

-1 1:-0.394668 2:-0.794872 3:-1 4:-0.871341 5:0.9365 6:0.75597
1 1:-0.463641 2:-0.897436 3:-1 4:-0.871341 5:0.44378 6:0.121824
1 1:-0.469432 2:-0.897436 3:-1 4:-0.871341 5:0.32668 6:0.302529
-1 1:-0.241547 2:-0.538462 3:-1 4:-0.871341 5:0.9994 6:0.987166
1 1:-0.757233 2:-0.948718 3:-1 4:-0.871341 5:-0.33904 6:0.915401
1 1:-0.167147 2:-0.589744 3:-1 4:-0.871341 5:0.95078 6:0.991566

The first column is class, and next 6 columns are features. I want to create 6 files for individual features. For example

feat1_file.txt will contain

 -1 1:-0.394668
  1 1:-0.463641
   ...
  1 1:-0.757233
  1 1:-0.167147

feat2_file.txt will contain

-1 2:-0.794872
...
1 2:-0.589744 

and so on. I have a Perl code that does this but it is horribly slow. Is there a way to do it faster? Typically the input files will contain 100K lines.

use strict;
use Data::Dumper;
use Carp;
my $input = $ARGV[0] || "myinput.txt";




my  $INFILE_file_name = $input;     # input file name

open ( INFILE, '<', $INFILE_file_name )
    or croak "$0 : failed to open input file $INFILE_file_name : $!\n";

    my $out1 = $input."_feat_1.txt";
    my $out2 = $input."_feat_2.txt";
    my $out3 = $input."_feat_3.txt";
    my $out4 = $input."_feat_4.txt";
    my $out5 = $input."_feat_5.txt";
    my $out6 = $input."_feat_6.txt";

    unlink($out1);
    unlink($out2);
    unlink($out3);
    unlink($out4);
    unlink($out5);
    unlink($out6);

    print "$out1\n";

while ( <INFILE> ) {
    chomp;
    my @els = split(/\s+/,$_);
    my $lbl = $els[0];

    my  $OUTFILE1_file_name = $out1;        # output file name
    open ( OUTFILE1, '>>', $OUTFILE1_file_name )
        or croak "$0 : failed to open output file $OUTFILE1_file_name : $!\n";
    print OUTFILE1 "$lbl $els[1]\n";
    close ( OUTFILE1 );         # close output file

    my  $OUTFILE2_file_name = $out2;        # output file name
    open ( OUTFILE2, '>>', $OUTFILE2_file_name )
        or croak "$0 : failed to open output file $OUTFILE2_file_name : $!\n";
    print OUTFILE2 "$lbl $els[2]\n";
    close ( OUTFILE2 );         # close output file

   # Etc.. until OUTFILE 6

}

close (INFILE);