New feature: "perlbrew install --switch $perl"

Automatically switches to the newly-installed Perl once installation
completes successfully.

This means that a good recommendation for newcomers to Perl who've installed
Perlbrew can be simply

    perlbrew install --switch stable

rather than

    perlbrew install 5.16.2
    perlbrew switch 5.16.2

The latter approach has the additional disadvantage that the appropriate
"latest stable Perl" version changes over time.

bin/perlbrew

@@ -203,6 +203,9 @@ Options for C<install> command:
     -j $n          Parallel building and testing. ex. C<perlbrew install -j 5 perl-5.14.2>
     -n --notest    Skip testing
 
+       --switch    Automatically switch to this Perl once successfully
+                   installed, as if with `perlbrew switch <version>`
+
        --as        Install the given version of perl by a name.
                    ex. C<perlbrew install perl-5.6.2 --as legacy-perl>
 

lib/App/perlbrew.pm

@@ -144,6 +144,7 @@ sub new {
         'help|h',
         'version',
         'root=s',
+        'switch',
 
         # options passed directly to Configure
         'D=s@',
@@ -868,6 +869,9 @@ sub run_command_install {
         die $help_message;
     }
 
+    $self->switch_to($installation_name)
+        if $self->{switch};
+
     return;
 }
 
@@ -1382,6 +1386,12 @@ sub run_command_switch {
         return;
     }
 
+    $self->switch_to($dist, $alias);
+}
+
+sub switch_to {
+    my ( $self, $dist, $alias ) = @_;
+
     die "Cannot use for alias something that starts with 'perl-'\n"
       if $alias && $alias =~ /^perl-/;
 

t/installation3.t

@@ -16,19 +16,27 @@ use Test::More;
         return map { "perl-$_" }
             qw<5.8.9 5.17.7 5.16.2 5.14.3 5.12.5 5.10.1>;
     }
+
+    sub App::perlbrew::switch_to {
+        shift->current_perl(shift);
+    }
 }
 
-plan tests => 2;
+plan tests => 3;
 
 {
-    my $app = App::perlbrew->new("install", "perl-stable");
+    my $app = App::perlbrew->new("install", "--switch", "perl-stable");
     $app->run;
 
     my @installed = $app->installed_perls;
     is 0+@installed, 1, "install perl-stable installs one perl";
 
     is $installed[0]{name}, "perl-5.16.2",
         "install perl-stable installs correct perl";
+
+    ok $installed[0]{is_current},
+        "install --switch automatically switches to the installed perl"
+            or diag explain $installed[0];
 }
 
 done_testing;