The following should do the trick ...

sub dateconvert       # converts dates from MMM-YY  ->   20YY/MM
{
  my %mon = ( "Jan" => 1, "Feb" => 2, "Mar" => 3, "Apr" => 4, "May" =>
+ 5, "Jun" => 6, "Jul" => 7, "Aug" => 8, "Sep" => 9, "Oct" => 10, "Nov
+" => 11, "Dec" => 12 );
  $_[0] =~ /(\w\w\w)\-(\d\d)/;
  return sprintf("20%02d.%02d",$2,$mon{$1});
}
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