use strict;
for my $lun ( ('SAN_VC0_42','SAN_VC0_43') ) {
    $luns_to_hdisk {$lun} = 
        { grep /hdisk\d+/, qx(vxdisk list $lun) } ;
}

print Dumper(\%luns_to_hdisk);

$VAR1 = {
          'SAN_VC0_43' => {
                            'hdisk855   state=enabled
' => 'hdisk920  state=enabled
',
                            'hdisk587   state=enabled
' => 'hdisk652  state=enabled
',
                            'hdisk51    state=enabled
' => 'hdisk116  state=enabled
',
                            'hdisk319   state=enabled
' => 'hdisk384  state=enabled
'
                          },
          'SAN_VC0_42' => {
                            'hdisk571   state=enabled
' => 'hdisk636  state=enabled
',
                            'hdisk35    state=enabled
' => 'hdisk100  state=enabled
',
                            'hdisk303   state=enabled
' => 'hdisk368  state=enabled
',
                            'hdisk839   state=enabled
' => 'hdisk904  state=enabled
'
                          }
        };