Because a variable only gets into scope *AFTER* the statement it's defined. That allows one to write: 
    my $var = $var;   # Start with the $var from the enclosing scope.
    local $_ = $_;

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So, in your example $bar comes into existance in the statement after the ?:.

Abigail

In reply to Re: Variable scope in ternary ?: operator not propagating? by Abigail-II
in thread Variable scope in ternary ?: operator not propagating? by JayBonci

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