If memory is not lacking, you can slurp the entire file and then process the lines, as in:

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


my $file = "/Path/to/file/file_X.txt";

open(my $fh, '<', $file) or die("Can not open file $file to read!\n");

my @lines = <$fh>;
close($fh);

for (@lines) {
    chomp;
    ## process the rest here, including calls to split    
}

print "\n# of lines: " . scalar(@lines) . "\n";
[download]

This has a good chance to speed things up, presumably because perl will make fewer calls to read(2).