--- a/.hgignore	Wed Dec 30 23:41:39 2015 +0100
+++ b/.hgignore	Wed Dec 30 23:42:56 2015 +0100
@@ -5,3 +5,4 @@
 ^_build/
 ^MYMETA.json$
 ^MYMETA.yml$
+^templates/version\.tt$

--- a/Build.PL	Wed Dec 30 23:41:39 2015 +0100
+++ b/Build.PL	Wed Dec 30 23:42:56 2015 +0100
@@ -6,6 +6,9 @@
     dist_abstract => 'once downloader',
     script_files => [qw(bin/once)],
     share_dir => [qw(templates)],
+    PL_files => {
+	'lib/version.PL' => 'templates/version.tt',
+    },
     requires => {
 	'perl' => '5.0.18',
         'File::MimeInfo' => 0,
@@ -13,10 +16,3 @@
 	'experimental' => 0,
     },
 )->create_build_script;
-
-# create the var.tt to be included
-mkdir 'templates.var' or -d 'templates.var' or die "templates.var: $!";
-chomp(my $version = `hg log -r . --template '{latesttag}-{latesttagdistance}-{node|short}\n'`);
-open(my $o, '>', $_ = 'templates.var/version.tt') or die "Can't open $_: $!\n";
-print $o qq{[% vcs.version = "$version"; %]\n};
-

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/version.PL	Wed Dec 30 23:42:56 2015 +0100
@@ -0,0 +1,6 @@
+#! /usr/bin/perl
+my $output = shift;
+chomp(my $version = `hg log -r . --template '{latesttag}-{latesttagdistance}-{node|short}\n'`);
+
+open(STDOUT, '>', $output) or die "Can't open $output: $!\n";
+print qq{[% vcs.version = "$version"; %]\n};