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in reply to How to localize conditionally?

local $ENV{BLAH} = condition ? 42 : $ENV{BLAH};

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Re^2: How to localize conditionally?
by ikegami (Patriarch) on Mar 14, 2011 at 14:28 UTC
    The library checks for existence, so that doesn't work. You'd need 
    local %ENV = condition ? (%ENV, BLAH=>42) : %ENV;

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      Did you test it? It works for me.

      - tye        

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        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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