use strict;
use warnings;

use constant USAGE => <<"EOT";
usage:
    perl $0  file_in  file_zero file_one
where:
    file_in     input file name
    file_zero   output file name - address[0] bit == 0
    file_one    output file name - address[0] bit == 1
EOT

die USAGE if @ARGV != 3;

my ($file_in, $file_zero, $file_one) = @ARGV;

open my $fh_in, '<', $file_in or die "opening '$file_in': $!";

open my $fh_0, '>', $file_zero or die "opening '$file_zero': $!";
open my $fh_1, '>', $file_one  or die "opening '$file_one': $!";

my $fh_current;

LINE:
while (my $line = <$fh_in>) {

    next LINE unless $line =~ m{ \S }xms;  # ignore blank lines

    my $got_command_addr =
    my ($rw_hex_addr) =
    $line =~ m{
      \A \d+ [.] \s+ command: (?: read | write) \s+ address:0x
      ([[:xdigit:]]+)
      \s* \Z
      }xms;

    if ($got_command_addr) {
        $fh_current =  0x1 & hex $rw_hex_addr ? $fh_1 : $fh_0;
        }

    die "no command read/write address seen" unless $fh_current;

    print $fh_current $line;

    }

close $fh_in or die "closing '$file_in': $!";
close $fh_0  or die "closing '$file_zero': $!";
close $fh_1  or die "closing '$file_one': $!";

exit;

# subroutines ######################################################

# none for now

##</code><code>##

c:\@Work\Perl\monks\syedasadali95>perl write_to_2_files_1.pl file_in.txt zero.txt one.txt

##</code><code>##

1. command:read address:0xA
7. command:read address:0xC

##</code><code>##

2. command:write address:0xB
3. writedata:0x12
4. writedata:0x34
5. writedata:0x56
6. writedata:0x78
8. command:write address:0xD
9. writedata:0x9A
10. writedata:0xBC
11. writedata:0xDE
12. writedata:0xF0