#!/usr/bin/perl

use strict;
use warnings;

my $file = '1140475.txt';;

open my $raw, '<', $file or die "open: $!";
open my $out, '>', "out_$file" or die "close: $!";

while ( my $line = <$raw> ) {
  chomp( $line );
  my @splits = split ( ',', $line );
  print $out "First line, first field: $splits[0]\n";
  last;
}

close $out or die "close: $!";

__END__