OK, so let's unpack what you did:

  for my $lun ( ('SAN_VC0_42','SAN_VC0_43') ) {
    $luns_to_hdisk {$lun} = { grep /hdisk\d+/, qx(vxdisk list $lun) } 
+;
  } ;
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• the qx(vxdisk list $lun) is invoked in List Context, so will return a list, each entry of which is one line as returned by the vxdisk command -- complete with line-ending.

• the grep returns a list which is a subset of the list returned by qx, selecting the entries which match /hdisk\d+/

• that is enclosed by {}, which in this case comprise an anonymous hash constructor -- constructing a hash with the even numbered entries that matched /hdisk\d+/ as keys, and the odd numbered entries as values.

• a reference to that anonymous hash is assigned to $luns_to_hdisk{$lun}

• that is done for $lun set to 'SAN_VC0_42' and then 'SAN_VC0_43'

so much, so straightforward.

I guess that's not what you intended ?

What did you have in mind ?

If you want $luns_to_hdisk{$lun} to be a list of the /hdisk\d+/ lines, you are very nearly there... you just need the anonymous list constructor [], not the anonymous hash constructor {}. That would be an HoL, though -- which is not what you were apparently wanting ?

You may want to consider a chomp somewhere or other to remove the line-endings from the selected lines. It's not clear whether you want the 'state=enabled' part, and if not you need a little extra code there.