local %ENV = condition ? (%ENV, BLAH=>42) : %ENV;
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Did you test it? It works for me.

- tye        

No, but how can one assign to a hash element that does not exist? Well, %ENV is magical, so let's test it out.

$ perl -wE'
   my $condition = 0;
   say exists($ENV{BLAH}) || 0;
   local $ENV{BLAH} = $condition ? 42 : $ENV{BLAH};
   say exists($ENV{BLAH}) || 0;
'
0
1
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So I was right

This is perl 5, version 12, subversion 2 (v5.12.2) built for i686-linu
+x
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