First of all I think your code has a bug in the while loop on one hand you are retrieving one record and storing it in the $trade variable, on the other hand when calling $action() you are retrieving another record so you are not processing half of the records with the $action and if your query returns only one record it won't get processed but it.

Secondly if you what to dump records I'd recommend you to use Data::Dumper, in the following form

UNTESTED

sub processTrades {
    my ($self,$action) = @_;
    my $count = 0;
    my $trdstmt = $self->_getTradesStatement();
    $trdstmt->bind_param(1,$self->{'startdate'});
    $trdstmt->bind_param(2,$self->{'enddate'});
    $trdstmt->execute(); 
    while(my $trade = $trdstmt->fetchrow_hashref()) {

        # Debug #
        use Data::Dumper;
        print STDERR Dumper($trade);
        # /Debug #

        &$action($trade); #Corrected#
        $count++;
    }
    return $count;
}
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• As evidenced by the call &$action($$trdstmt->fetchrow_hashref());, $action is a code ref, though I'd need to see more code to determine is it is an anonymous sub. I'd also have to see more code to know what it does.
• Based on the structure, I'm guessing that $trade in the while-loop contains your database return. A simple way to examine its contents should be to use Data::Dumper, a la:

      while(my $trade = $trdstmt->fetchrow_hashref()) {
          print Dumper $trade;
          &$action(%$trade);
          $count++;
      }
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  after adding use Data::Dumper; to your code.
• I am guessing based on syntax that $self is a DBI database handle. Assuming this is the case, I would suggest instrumenting to test for success on your database calls. Perhaps something like:

      $trdstmt->bind_param(1,$self->{'startdate'}) or die "Bind failed: 
  +$DBI::errstr";
      $trdstmt->bind_param(2,$self->{'enddate'}) or die "Bind failed: $D
  +BI::errstr";
      $trdstmt->execute() or die "Execute: $DBI::errstr";
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• For a reasonable review of Perl approaches to tackle this task, read Basic debugging checklist.

Update: Note the bug caught by bluescreen below.

hsweet:

Run the program in debug mode, set a breakpoint before the call, and then step through it. Then you'll be able to find out which subroutine is executing and examine the data you want. It's pretty simple, really:

roboticus@Boink> # Execute script under debugger:
roboticus@Boink> perl -d genfiles.pl

Loading DB routines from perl5db.pl version 1.32
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(genfiles.pl:5):    for (1 ... 50000) {
  DB<1> # Set breakpoint on line 7

  DB<2> b 7
  DB<3> # Execute (continue) until end or breakpoint

  DB<4> c
main::(genfiles.pl:7):        my $u = join('',('A'..'Z')[rand 26, rand
+ 26, rand 26]);
  DB<4>
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As the debugger startup message says, use 'h' for help.

...roboticus

Time flies like an arrow. Fruit flies like a banana. Groucho Marx