Why not try swapping line 7 to something like this? 
my $x = $bar{'one'};
$x .= " $foo{'one'}";

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That way if there IS an uninitialized variable error, you'll be able to tell which variable it is based on the line number returned.
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In reply to Re: Debugging "Use of uninitialized value" warnings. by Spidy
in thread Debugging "Use of uninitialized value" warnings. by cwry

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