for my $dc (@default_columns) {
    $dc =~ s/([A-Z])/_\l$1/g;
    $allowed_columns{$dc} = 1;
}

##</code><code>##

for my $dc (@default_columns) {
    my $t;
    ($t=$dc) =~ s/([A-Z])/_\l$1/g;
    $allowed_columns{$t} = 1;
}