Personally, I don't like how you're setting $where_statement, with all those additional appends. I'd prefer to use a HERE doc for multi-line chunks of embedded source code, e.g.

my $dt_min = $format_date->format_datetime( $dt_set->min );
my $dt_max = $format_date->format_datetime( $dt_set->max );

my $where_statement = <<EOF;
 where ir.ir_id = cm.call_master_id and 
 ir.closed_date is not NULL and 
(ir.closed_date >= '$dt_min' and
 ir.closed_date < '$dt_max' ) and cm.user_id = ? 
EOF
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JMHO, of course.