You can check the existence of minus sign and then prepend the output if necessary. 
$total = sprintf("%s%.2f", @TFCNTL_Tax[$i] =~ /(\-)/ ? $1 : undef, @TF
+CNTL_Tax[$i]);

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In reply to Re: Proper creation of a negative number by pme
in thread Proper creation of a negative number by insta.gator

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