In addition to javafan and BioLion responses, you need to clarify if these "three variables" are simple variables like numbers or shortish strings--in which case they can potentially be transfered via the command line.

Or are they complex variables (like arrays or hashes) which would require the use of pipes or IO::Sockets and perhaps Storable; or something more complex.

The master script to run:

#!/usr/bin/perl
use warnings;
use strict;
use IPC::Open3;


my $pid = open3(\*WRITE, \*READ,0, './myslave1');
            #if \*ERROR is false, STDERR is sent to STDOUT 

while (1){
#send something to slave
my $test = time;
my $str = $test x 50;
print WRITE "$str\n\n\n\n";

#get the answer from slave
my $buf;
sysread(READ,$buf,1024);

print "$test = $buf\n";

sleep 1;
}
waitpid($pid, 1);
# It is important to waitpid on your child process,  
# otherwise zombies could be created.
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and the myslave1 script

#!/usr/bin/perl
use warnings;
use strict;
use IO::Select;

my $timeout = 1;

my $s = IO::Select->new();
$s->add( \*STDIN );

while (1) {
    if ( my @ready = $s->can_read($timeout) ) {

        # we got input
        for my $fh (@ready) {
               my $input;
               sysread( $fh, $input, 1024);
                                          
           #do some processing, for example
           syswrite(STDOUT, "processed: $input");
        }
    }
}
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Use system, exec or backticks to call the other program, and pass the values as commandline args, you can then read command line arguments in the other script. You probably don't want to get into shared variables and memory... HTH

As for "sending", what to do depends on what you want. Does the first script start the other? Or are both scripts running by the time you want to exchange values? Or perhaps the second script doesn't start running long after the first one finished? Are they running on the same machine?

There are several ways of Inter Process Communication discussed in the perlipc manual page. Doesn't any of them work for you?

Don't; you're making your life too complicated.

Turn both programs into modules and then use them from the same program. Call functions in one module from another module.

That seems like more work up front, but it's much less fragile and system dependent.