in reply to eval, Read environment variable and expand using eval

it didn;t work
Please elaborate. It seems to work for me when I run your 2nd code example. Here is the output I get: 
$r = (defined $ENV{HOST} ? $ENV{HOST} : 'sqlhost')

sqlhost

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What do you expect the output to be? First, you print the statement verbatim, then you print the eval'd statement. I do not have the HOST variable set.

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Re^2: eval, Read environment variable and expand using eval
by tart (Beadle) on Feb 19, 2010 at 04:34 UTC
    There must be something which I don't know, In second code the output I am getting is,
    $r = (defined $ENV{INFORMIXSQLHOSTS} ? $ENV{INFORMIXSQLHOSTS} : 'sqlhost')
    But I am expecting,
    sqlhost
    which I am getting from first code. Cheers, Thanks
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      You should be getting that since you're printing $stmt. You should *also* be getting the value of $ENV{HOST} or sqlhost.
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        Remember that an environment variable can be defined yet empty. In sh:
        MYVAR=

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        In perl:
        $ENV{MYVAR} = "";

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      There is a subtle yet important difference between defined and exists on hash and array elements. Defined will autovivify your hash element and make its value undefined.

      Perhaps you meant this?

      $r = (exists $ENV{INFORMIXSQLHOSTS}) ? $ENV{INFORMIXSQLHOSTS} : 'sqlho
+st')

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      If you want to check every possiblity this would be the best. However I usually just do the exists() check.

      $r = ((exists $ENV{INFORMIXSQLHOSTS} && defined($ENV{INFORMIXSQLHOSTS}
+) && length($ENV{INFORMIXSQLHOSTS})  ) ? $ENV{INFORMIXSQLHOSTS} :  's
+qlhost'));

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        No, defined does not autovivify 
        my %f;
warn snot => defined $f{snot};
warn snot => exists $f{snot};
__END__
snot at - line 3.
snot at - line 4.

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