use strict;
use warnings;

use feature qw{ say };

my $str      =  q{  Intel(R) Xeon(R) CPU          X5660  2.80GHz };
my $rxSpaces = qr{(?x)  # Use regex extended syntax to allow comments
   (?:                  # Open non-capturing group for alternation
      (?<= \A ) \s+     # Spaces preceded by beginning of string
      |                 # or
      (?<= \s ) \s+     # Spaces preceded by a single space
      |                 # or
      \s+ (?= \z )      # Spaces followed by end of string
   )                    # Close group
   };

# Replace matching spaces by nothing globally.
#
$str =~ s{$rxSpaces}{}g;
say qq{-->$str<--};

##</code><code>##

-->Intel(R) Xeon(R) CPU X5660 2.80GHz<--