I crave some benevolence from the monks. I'm tying to teach myself some basic text parsing. I'm trying to test for if a part of a month exists in a string, having split the string into tokens and then the tokens into substring of 3 characters long. If it does exist, then I'm trying to swap it to a number using a hash. I keep getting a use of an uninitialised value in the concatenation. 
sub num_month {
  my $date = shift;
    
  my %months  = (JAN => '01', FEB => '02', MAR => '03', 
                APR => '04', MAY=> '05', JUN => '06', 
                JUL => '07', AUG => '08', SEP => '09', 
                OCT => '10', NOV => '11', DEC => '12');
                
  my @tokens = split (" ", $date);
  my $date;
  foreach my $num (@tokens) {
     my $strBegin = substr($num, 0, 3);
     my $date =~ s/$strBegin/$months{uc $strBegin}/;  
  }
  return $date;
}

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As this pattern may or may not exist in the line, I just wanted to effect a light swap using a hash rather than trying to call Date::parse since there is no standard pattern.

In reply to A quick date swap from a string by Quicksilver

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