Note that  split / +/, $string doesn't handle leading whitespace gracefully:

c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"my $CPU = '  Intel(R) Xeon(R) CPU          X5660  2.80GHz   ';
 dd $CPU;
 ;;
 my @CPU_SPLIT = split / +/, $CPU;
 dd \@CPU_SPLIT;
 ;;
 my $t = join ' ', @CPU_SPLIT;
 dd $t;
"
"  Intel(R) Xeon(R) CPU          X5660  2.80GHz   "

["", "Intel(R)", "Xeon(R)", "CPU", "X5660", "2.80GHz"]

" Intel(R) Xeon(R) CPU X5660 2.80GHz"
[download]

Here, the special-case  ' ' split pattern is better (if you're going to split/join):

c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"my $CPU = '  Intel(R) Xeon(R) CPU          X5660  2.80GHz   ';
 dd $CPU;
 ;;
 my @CPU_SPLIT = split ' ', $CPU;
 dd \@CPU_SPLIT;
 ;;
 my $t = join ' ', @CPU_SPLIT;
 dd $t;
"
"  Intel(R) Xeon(R) CPU          X5660  2.80GHz   "

["Intel(R)", "Xeon(R)", "CPU", "X5660", "2.80GHz"]

"Intel(R) Xeon(R) CPU X5660 2.80GHz"
[download]

(Dealing with general whitespace was exactly why  ' ' was special-cased.)