use strict;
use warnings;

use autodie qw( open close );
use English qw( -no_match_vars );

@ARGV == 1 or die "Usage: perl $PROGRAM_NAME <input file>\n";

my $input_file = shift;

open my $fh, '<:encoding(ASCII)', $input_file;

RECORD:
while (my $record = <$fh>) {
    # Do something with record...
}

close $fh;