Tue, 01 Jan 2008
Perl 5.10 - My Favourite Three Features
Since the release of Perl 5.10 (back on 2007/12/18) there have been a fair
few articles discussing all the shiny new features - including smart matching, a
built-in switch and state variables but my favourite three haven't really
received much coverage. So I'll add to the pile of blog posts.
First up is a tiny (from the outside anyway) change that may have the biggest impact of all the new features on my day to day perl - the display of the actual name of uninitialized variables.
# older perls
$ perl584 -we 'print $foo, "\n";'
Use of uninitialized value in print at -e line 1.
# perl 5.10
$ perl510 -we 'print $foo, "\n";'
Use of uninitialized value $foo in print at -e line 1.
From the perspective of someone who has to spend the occasional afternoon reading Apache errorlogs I really like this one.
Now we move on to stackable file tests; something I was surprised perl couldn't do when I first noticed it was missing years ago -
# older perls
...
if (-s $file && -r _ && -x _) {
print "$file isn't zero length and is +rx\n";
}
...
# perl 5.10
...
if (-s -r -x $file) {
print "$file isn't zero length and is +rx\n";
}
...
Lastly on my little list is named captures - instead of referencing
$1 and $2 etc. you can now assign them names at
the point of capture and then pull the values out of a hash at a later time
-
# requires 5.10 or above. But not 6.
my %date;
my $sample_date = '20071225';
if ( $sample_date =~ /(?<year>\d{4})(?<month>\d{2})(?<day>\d{2})/ ) {
%date = %+;
}
say "The year is $date{'year'}";
While none of these are massive attention grabbing additions like the powerful smart matching, switch statement or say (one of those is not like the others ;)) they help make the day-to-day stuff a little more pleasant.
Bonus feature -
my $x;
my $default = 'foo';
$x = 0;
$x ||= $default;
say "\$x is $x";
$x = 0;
$x //= $default;
say "\$x is $x";
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Posted: 2008/01/01 11:59 | /perl | Permanent link to this entry | This entry + same date
Copyright © 2000-2005 Dean Wilson
