Perl Search and Replace, using variables

Perl is a reasonable scripting language (as are others, so shh!). It has always had strong regular expression support; those regular expressions can also be used to do substitutions, such as:

my $pet = "I have a dog";
$pet =~ s/dog/cat/;

Neat enough. But lets say I want to look up the parts of the “s///” that define my search text, and my replacement text. Easy enough:

my $pet = "I have a dog";
my $search = "dog";
my $replace = "cat";
$pet =~ s/$search/$replace/;

But lets make our substitution a little more complex – I want to match a URL, and have the host and port lower case, but leave the path as the case it comes in, and I don’t want to be entering expressions as the replacement text! Lets try:

my $url = 'http://www.FOo.COm/wibbLE';
my $search = '^([^:]+://[^/]+)/?(.*)?$';
my $replace = '\L$1\E/$2';
print $url if $url =~ s/$search/$replace/;

Sadly, while $search matches, the replace is the string “\L$1\E/$2“. It appears that we need to use a combination of “/e” mode (evaluate as expression) to evaluage this replacement string. Of course, when we’re doing eval, we want to ensure we don’t have malicious content in $replace, such as “unlink()” and friends who could do Bad Things. So my solution was to escape double quotes from my $replace string, wrap that all in double quotes, and pass in “/ee“:

my $search = '^([^:]+://[^/]+(:\d+)?)/?(.*)?$'; # From database
my $replace = '\L$1\E/$3'; # From database
$replace =~ s/"/\\"/g; # Protection from embedded code
$replace = '"' . $replace . '"'; # Put in a string for /ee
print $url if $url =~ s/$search/$replace/ee;

This will give us:

  • Port and host name lower case
  • Hostname (and port) will always have a slash after it
  • Bad code like unlink() won’t be run
  • The expression that we initally set/fetch/got in $replace is just a vanilla replacement term, not arbitary Perl code.

Acer Aspire Revo 3700 with Linux

Looks like Acer is releasing a Linux model of its new Revo, product code “PT.SEMEC.003“; listed as a 160 GB HDD, 2 GB Linux version. Insight UK have them for £230. See this list of sites for prices; all around £200 – £300.  Gigabit ethernet sees nice, as does 802.11n if you need to fall back to wireless. Amazon ar elisting it for £349, so a little steep there. Here’s the press release from Acer, dated September 9.

HP Dreamscreen update: 23 Sept 2010 (

Yesterday, the 10th of October 2010 (10-10-10), my HP DreamScreen dutifylly informed me of a firmware update! Wow, I wasn’t expecting any more updates out of HP, given the age of the product. Down came, with a release/build date of “9/23/10“, and on boot telling me that to use the Facebook app there were new security options in Facebook to permit this. It claims to be fron the “HP Development Company”. Is that separate from HP? Googling around shows “Hp Development Company LLC is located at 4401 N Mesa St El Paso, TX 79902″. Hm.

Snapfish deleting photos

I started using Snapfish to store photos as the only main way to get an online album displying in my HP DreamScreen. HP decided against supporting Flickr, Picasa, or other established sites, opting to use Snapfish because – HP owns them. Fair enough, so I signed up and uploaded some content to show on my Hp DreamScreen device(s). Now, Snapfish have told me:

Please place an order by October 12, 2010 or you risk losing your photos. Lastly, remember you can also preserve your photos with a photo CD.

Thanks HP; you’ll delete my content since I havent purchased prints from you. How else can I display an album online to the display I purchased from you? Can I get an app for Flickr, Picasa, or perhaps access to boot and run my own code on here yet? The platform appears to be stagnant now for some time….