First suggestion: Use the special <CODE> tags around your code. Notice how your while clause got munged, that won't happen with code enclosed in <code> tags...

Second suggestion: The regex line in cpu_stat can be shortened... Since a m// regex returns ($1,$2,$3,etc) when called in list context, you can shorten that line to:

($cpu_user, $cpu_nice, $cpu_total, $cpu_idle) = /^cpu\s+(\d+)\ (\d+) (
+\d+) (\d+)/;
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Third suggestion, since you aren't actually doing anything with the individual values in the subroutine, don't even bother with multiple scalars... just use an array. Fourth: while seems overkill since you aren't really looping. Just grab one line w/o a loop.

Fifth: you can also remove the backslash before the space in your regex...

sub cpu_stats {
   my @cpustats;

   open STAT_FILE, "/proc/stat" or warn "Couldn't open /proc/stat: $!\
+n";
   my $line = <STAT_FILE>;

   @cpustats = $line =~ /^cpu\s+(\d+) (\d+) (\d+) (\d+)/;
   close STAT_FILE;

   return(@cpustats);
}
[download]

-Blake