fglock, and the others, are correct. Here is my version of your last 3 print statements:

print qq|testing: $flat[1], $flong[1]\n|;
print qq|testing: $fval{"39.750000"}{"-179.000000"}\n|;
print qq|testing: $fval{"$flat[1]"}{"$flong[1]"}\n|;
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The "qq" operator lets you use whatever you want to use as the delimiter of the string - I chose to use the pipe(|) since the string itself contains double quotes, *and* my other favoite choice for qq operator, {}. HTH.