#!/usr/bin/perl -w

# Strict
use strict;
use warnings;

# Libraries
use IO::File;
use IO::Select;
use IPC::Open3 qw/ open3 /;

# Constants
use constant BLOCK_SIZE => 4096;

# User-defined
my $module = "server";
my $OLD    = "1.41";
my $NEW    = "1.42";
my $cmd    = "cvs rlog -r${OLD}::${NEW} -SN $module";
my $outbuf = "";
my $errbuf = "";

####################
### Main program ###
####################
my ($pout, $perr) = run_command($cmd);

# Verify data
print "\n[STDOUT]\n"; map { print "\e[102m$_\e[m\n" } @$pout;
print "\n[STDERR]\n"; map { print "\e[101m$_\e[m\n" } @$perr;

# Now do whatever you want to with the data $pout and $perr ...

###################
### Subroutines ###
###################
sub run_command {
    my ($cmd) = @_;

    my $errfh = IO::File::new();
    my $pid   = open3(my $infh, my $outfh, $errfh, $cmd);
    my $r_sel = IO::Select->new($outfh, $errfh);
    my $pfh   = { $outfh => [ ], $errfh => [ ] };

    while ($r_sel->handles()) {
        my @can_read = $r_sel->can_read(0);
        foreach my $fh (@can_read) {
            my $pbuf = $pfh->{$fh};
            my $rv = sysread($fh, my $text, BLOCK_SIZE);
            (defined $rv) or die "Failed cmd '$cmd' ($!)\n";
            $rv or $r_sel->remove($fh);
            push @$pbuf, $text;
        }
    }

    waitpid($pid, 0);
    my $pout = [ split(/\n/, join("", @{$pfh->{$outfh}})) ];
    my $perr = [ split(/\n/, join("", @{$pfh->{$errfh}})) ];
    return ($pout, $perr);
}