$* replacement

So, the special variable $* has been removed from perl 5.10, after having been deprecated for years. For those who don't remember Perl4-style programming, $* was used to enable multi-line matching in regular expressions. In Perl 5, the preferred way to do it is to use the more flexible regexp flag /m.

I removed that poor old variable not because I like removing old things, but because it was standing in the way of a bug I wanted to fix (bug #22354). Anyway. Apparently there is still out there some old Perl code that fears not using $*. And notably ghc's evil mangler, which broke with perl 5.9.5.

But Audrey Tang (who else?) found an elegant way to emulate $* = 1, in a characteristic perl-zen manner. Here's how: the current evil mangler contains this simple line of code, in a BEGIN block:

require overload; overload::constant( qr => sub { "(?m:$_[1])" } );

Saving GNOME settings

Here's a small tip I got from GNOME expert Pascal Terjan, and that I'm copying here because I don't trust my memory:

Want to inspect the settings of some GNOME application? Use gconf-editor.

Want to copy the settings of some GNOME app (like, say, metacity) from one desktop to another? Use the command-line tool gconftool, specifically the options --dump and --load. (The paths you need to feed to gconftool can be retrieved via gconf-editor.)

Munin plugin for ping response time

My ADSL router (a freebox) shows a recent tendency to desynchronize itself. That's annoying, even it that only lasts a few minutes from time to time. Maybe a cable needs to be replaced (advice?). So, I quickly hacked this plugin for Munin, an excellent system monitoring package:

#!/usr/bin/perl -wT

use strict;

our @HOSTS = qw(free.fr);
if (@ARGV && $ARGV[0] eq 'config') {
    print <<CONFIG;
graph_title Ping response time
graph_vlabel time (ms)
graph_args --base 1000 -l 0
graph_scale no
graph_category network
CONFIG
    for my $host (@HOSTS) {
        my $name = $host;
        $name =~ tr/./_/;
        print "$name.label $host\n";
    }
}
else {
    @ENV{qw(PATH)} = qw(/bin);
    for my $host (@HOSTS) {
        my $name = $host;
        $name =~ tr/./_/;
        my @ping = qx(/bin/ping -nc1 $host 2>/dev/null);
        my $times = $ping[-1];
        my $val = '';
        if ($times =~ m{^rtt min/avg/max/mdev = ([\d.]+)}) {
            $val = $1;
        }
        print "$name.value $val\n";
    }
}

Feel free to adapt/improve. This code is of course released under whatever license Munin is released under (I didn't bother to check.)

Perl 5.9.5

I've released Perl 5.9.5 on saturday. Get it while it's hot. Get the official announcement as well.

Sub::Current

I've released another new heavily magic Perl module on CPAN, this time scratching an itch of Yves Orton. It's called Sub::Current and allows you to get a reference to the currently executing subroutine.

At first I wanted to use a tied scalar instead of a function to get this reference; however, due to the way parameter passing is implemented in Perl, that's not easily possible: the tied variable (let's call it ${^ROUTINE}) is FETCHed at the innermost scope, so this won't work:

sub foo {
    # here ${^ROUTINE} points to bar(), not to foo() !
    bar( ${^ROUTINE} );
}

I think that could be done by tweaking some of the ck_ functions that are used to optimize Perl's internal optree during the compilation phase. I know that some people are not afraid to do this, but I feel that this would be a rather fragile solution, for only a little bit of syntactic sugar.