JayK's code samples

Given a 2d table - remove all empty columns

The following code searches a 2d hash (aka table) to determine if a particular column in every row is empty. It has the advantage of speeding up as it works because once it determines that a column is not empty for one row, it will never check that column again.

my %empty_columns = map { $_ => 1 } @column_names;

foreach my $row (keys %table) { 
     foreach my $column (keys %empty_columns) {
         if ($table{$row}->{$column} ne '') {
             delete($empty_columns{$column});
         }
     }
}

# don't bother to do the delete if we don't have
if (keys %empty_columns) {
    foreach my $row ($keys %table) {
       foreach my $column (keys %empty_columns) {
           delete($table{$row}->{$column});
       }
    }
}