You didn't say what part of it your team is having difficulty understanding, so here's a basic rundown of what is going on:

sub get_abandonned($) {                                # Subroutine de
+finition.
  my $dnis = shift;                                    # $dnis will ho
+ld
                                                       # the parameter
+.

  my $total = 0;                                       # $total holds 
+0.

  for my $key(keys %all_calls) {                       # There is a ha
+sh named
                                                       # %all_calls.  
+Iterate
                                                       # over the keys
+ of the
                                                       # hash and assi
+gn each
                                                       # key to $key o
+n its
                                                       # respective it
+eration.

    next if ($key =~ /duplicate/);                     # Proceed to ne
+xt
                                                       # iteration if 
+the
                                                       # current key c
+ontains
                                                       # the text 'dup
+licate'.

    if(                                                # If all of the
                                                       # following are
+ true:
         $all_calls{$key}->[DNIS] eq $dnis
      && $all_calls{$key}->[SPEECH] == 0
      && $all_calls{$key}->[TRANSFER] eq "hungup"
    ) {                                                # then do the f
+ollowing:

      my $time_length                                  # Give a value 
+to
                                                       # time_length,
        = &get_call_length($all_calls{$key}->[TIME]);  # from this fun
+ction
                                                       # call.

      if($time_length <= -29) {                        # Now if this i
+s true...
        $total++;                                      # increment $to
+tal.
      }
    }
  }                                                    # Move on to ne
+xt key.
  return $total;                                       # return the $t
+otal.
}
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update

I tried to decipher your code and there is nothing particular "perlish" that we could explain. A hash of (phone?)"calls" is traversed and filtered by different criterias.

Maybe you should hire someone who understands your business logic and algorithms in general.

An approximate translation, note I'm inferring/guessing a few things (such as that %all_calls contains a set of call records):

• The function get_abandonned takes one argument, I'm guessing this is some kind of identifier (DNIS = Dialed Number Identification Service?)
• It loops over the set of call records in %all_calls, skipping those whose key contains the string "duplicate", and selecting those where the "DNIS" item in the record matches the one given to the function as an argument and whose "SPEECH" value is zero and whose "TRANSFER" value is "hungup"
• For each of those records, it calls the function get_call_length, giving it the "TIME" item from the call record; if the value that the function returns is less than or equal to -29, increment the "total" counter by one.
• After having processed all the records, the function returns the "total" counter.

A note on the apparent data structure: %all_calls is a hash that contains a set of key/value pairs, where the keys sometimes contain the word "duplicate" (can't tell more than that from this code), and the values are arrays (arrayrefs to be more specific). I'm guessing that DNIS, SPEECH, etc. are integer constants are the indices of those arrays.

This section of code is supposed to count abandoned calls. Your explanation makes complete sense. Thank you so much!