system() doesn't return the output, just the exit status. There are other ways of executing programs that will give you the exit status. For instance, use open() with a pipe:

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);
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Backticks and qx// also work:

my $input = `ps -deaf | grep httpd | grep -v grep | wc -l`;
my $input2 = qx/ps -deaf | grep httpd | grep -v grep | wc -l/; # Same 
+thing
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Reinvent a rounder wheel.

Note: All code is untested, unless otherwise stated