sweetblood:

Line 17 is your problem--you're reassigning the hash, rather than just adding to it. Change this:

     %mdata = (
        $pkey => {
        ABC  => trim_trailing($rec[1]),
        DESC => trim_trailing($rec[2]),
        UNIT => trim_trailing($rec[3]),
        LOC  => trim_trailing($rec[4])
        }
     )
[download]

to this:

     $mdata{$pkey} = {
        ABC  => trim_trailing($rec[1]),
        DESC => trim_trailing($rec[2]),
        UNIT => trim_trailing($rec[3]),
        LOC  => trim_trailing($rec[4])
     };
[download]

While you're at it, I'd suggest changing:

    next unless (s/\^/\^/g == 4);
    my @rec = split /\^/;
[download]

to:

    my @rec = split /\^/;
    next unless @rec == 5;
[download]

...roboticus

When your only tool is a hammer, all problems look like your thumb.