Shell Programming and Scripting

open(OUTPUT, 'perl myscript.pl file1 |');
close OUTPUT;
open(OUTPUT, ">> file2");
close OUTPUT;

open(OUTPUT1, 'perl myscript.pl file1 |');
open(OUTPUT2, ">> file2");
close OUTPUT1;
close OUTPUT2;

perl myscript.pl file1 >>file2

open (INPUT, 'perl myscript.pl file1 |') or die "$!\n";
open (OUTPUT, ">>file2") or die "$!\n";
while (<INPUT>) { # read a line of input from myscript.pl
  print OUTPUT;  # print it to the output handle
}
close INPUT;
close OUTPUT;

$num = 0;

while ($num <= $#arr_y ) {
        open(FH,"< file2") or die $!;
        print "@LISTING[$num] is undercheck now.\n";
                while( <FH> ) {
                chomp;
                if($_ =~ @LISTING[$num] && $_ =~ @SLIST[$num]) {
                        $check_file = "already_appended"
                        };
                close FH;
                print "@arr_y[$num]\n";
                if($check_file ne 'already_appended') {
                        open(INPUT, 'perl myscript.pl @arr_y[$num] |');
                        open(OUTPUT, ">> file2");
                        while (<INPUT>) {       # read a line of input from myscript.pl
                                print OUTPUT;   # print it to the output handle
                        }                       
                        close INPUT;
                        close OUTPUT; 
                        print "@LISTING[$num] will be appended.\n"
                }
                else
                {
                        print "@LISTING[$num] will NOT be appended.\n";
                };
                };
        $num = $num + 1;
};
};

my $command = "perl scriptname.pl @args | ";

my $pipe_des;
open($pipe_des, $command) or die "Unable to open pipe command : $command <$!> \n";