system("pvscan>>pv.txt1");
open my $FH,"pv.txt1"  or die "Cannot open file: $!";
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I see that you append to the pv.txt1 file which means more lines to parse every time you run the script; is this actually intended? Unless you want to keep the output of pvscan hanging around you can open a file handle directly on piped commands. Something like:-

open my $pvscanFH, '-|', 'pvscan'
   or die "Cannot fork pvscan: $!\n";
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You can then read the command output line by line just as if it was a file on disk.

I hope this is helpful.