Without a small sample of your input file, it is not simple to reproduce your results. Try to print both values before your "if" line: 
print "julday >>>$julday<<<\n";
print "julday_old >>>$julday_old<<<\n";

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Are these values integers, or are they floating point values?

Isn't... 

  if(! ($julday == $julday_old)){

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the same as...? 

  if ($julday != $julday_old){

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In reply to Re: printf in if-statement by toolic
in thread printf in if-statement by Utrecht

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