use strict;
use warnings;

while (<DATA>){

    # Returns true after matching "LV Name",
    # and returns false after
    # matching "--- Logical extents ---".
    if (/^LV Name/ .. /--- Logical extents ---/){
        print "$_";
    }


}

__DATA__
Line above
--- Logical volumes ---
LV Name                     /dev/vg00/lvol3
VG Name                     /dev/vg00
LV Permission               read/write
...
   --- Logical extents ---
Line below