Thanks for the great advice.
I'm still stuck, though, on how to loop through this list from the calling sub.

sub TSM_Enquire {
  my $Slot, $Type, $Label;

  open(IN,"/bbs/rtscripts/adsm_cmd q libv|");

  while (<IN>) {
    next unless (/3584/);
    s/,//;
    @Fields = split ' ';
    $Label = $Fields[2];
    $Slot = $Fields[$#Fields-1];
    $Type = $Fields[3];
    push @List, "$Slot $Type $Label";
  }

  close(IN);
  return @List;
}

sub Process_Columns {
  my $Count=0;
  my $Simple;
  my @Column_Info = ( [ 1024, 1067 ],     # Column 1 start stop
                      [ 1068, 1093 ],     # Column 2 start stop
                      [ 1094, 1137 ],     # Column 3 start stop
                      [ 1138, 1163 ],     # Column 4 start stop
                      [ 1164, 1207 ],     # Column 5 start stop
                      [ 1208, 1233 ],     # Column 6 start stop
                      [ 1234, 1277 ],     # Column 7 start stop
                      [ 1278, 1321 ] );   # Column 8 start stop

  if ($LibraryType =~ "tsm") {
     @List = TSM_Enquire;
  } else {
     @List = Tapeutil_Enquire;
  }

  for ($Count=1;$Count<=8;$Count++) { # Traverse columns
    my $StartPos = $Column_Info[$Count][1];
    my $Pos = $StartPos; 
    my $Column_Count = 0;
    my $EndPos = $Column_Info[$Count][2];
    my $NewPos=0;
    my $NewLabel="";
    my $NewRec="";

    while ($NewRec = @List) {
      chomp $NewRec;
      $NewRec =~ s/^ //;
      ($Pos, $Type, $Label) = split(' ', $NewRec, 9999);
      for ($I=1;$I<=($EndPos-$StartPos)+1;$I++) {
<snip>
[download]

I that the above is wrong (because it doesn't work, read as: doesn't do what I want).
Any ideas, comments, etc?
TIA
coec