# prepare regex sub-expressions
  my $sizerx = '(-|\d+(\.\d+)?[GM]?)'; # Matches '-', or a float + 'M' or 'G' for size
  my $loadrx = '(-|\d+\.\d\d)'; # Matches '-' or a float
  my $procrx = '(-|\d+)';      # matches '-' or an integer

  # Test the line to see if it matches
  if( $_ =~ /^(\w+)\s+    # host
              (\w+)\s+    # os
              $procrx\s+  # nproc
              $loadrx\s+  # load
              $sizerx\s+  # memtot
              $sizerx\s+  # memuse
              $sizerx     # swapto
              \s*$
            /x 
  ) {
    print "using regex, host is [$1]\n"; 
  }