open(EXEC, '-|', 
    'ps', '-deaf | ', 'grep', 'httpd |', 'grep', 
    '-v', 'grep |', 'wc', '-l') 
    or die "Can't exec: $!\n";

# Now read the output just like a file
while(my $line = <EXEC>) {
    chomp $line;
    print "$line\n";
}
close(EXEC);