#!/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__

##</code><code>##

$ cat out_1140475.txt 
First line, first field: 1424621700

##</code><code>##

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

use Path::Tiny qw/ path /;

my $file = '1140475.txt';

my $first = ( split ',', (path($file)->lines( {chomp => 1, count => 1} ))[0] )[0];

print "$first\n";

__END__

##</code><code>##

$ perl 1140475-2.pl
1424621700
$