If you can use Storable you can try the following:

#!/usr/local/bin/perl -w
use strict;
use Fcntl;   # For O_RDWR, O_CREAT, etc.
use SDBM_File;
use Storable qw/freeze thaw/;

...


sub insert {
    my $table_name = shift;
    my $col_vals    = shift; # ref to hash

    my %h;
    tie(%h, 'SDBM_File', $table_name, O_WRONLY , 0666) 
    or die "Couldn't tie SDBM file $table_name: $!; aborting";
    $h{$col_vals->{REQ}} = freeze $col_vals;
    untie %h;    
}

sub select_all {
    my $table_name = shift;
    my %h;
    tie(%h, 'SDBM_File', $table_name, O_RDONLY  , 0666) 
    or die "Couldn't tie SDBM file $table_name: $!; aborting";

    for my $i ( keys %h ) {
    my $row = thaw $h{$i};
     print $i," -> ";
    while (my ($key,$val) = each %$row) {
        $val = 'undef' unless $val;
        print "\t", $key, ' = ', $val, "\n";
    }
    }
}

...
[download]

this uses the value of the key 'REQ' as the primary key, and then freezes the hash so it can be stored in the SDBM_File. The select_all sub uses thaw to deserialize the hash into a hash ref containing the 'row' of values.

HTH!

--
hiseldl
What time is it? It's Camel Time!