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perl/Examples/Chap9/Environment.pm

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+
+
+###
+### Environment.pm
+###
+
+## Chapter 9 section 4.3.2
+
+sub subset {
+  my ($self, $name) = @_;
+  my %result;
+  for my $k (keys %$self) {
+    my $kk = $k;
+    if ($kk =~ s/^\Q$name.//) {
+      $result{$kk} = $self->{$k};
+    }
+  }
+  $self->new(%result);
+}