my $csv = Text::CSV_XS->new ({ binary => 1, auto_diag => 1});
my @hdr;
while (my $row = $csv->getline ($fh)) {
    # example:
    if ( # a change in number of columns
         @hdr != @$row
         or
         # first column matches header criterium
         $row->[0] =~ m/^[A-Z]/
         ) {
        @hdr = @{$row};
        next;
        }
    # just an example
    my %hash;
    @hash{@hdr} = @$row;
    }