Shell Programming and Scripting

    open (INFO, "temp.txt") or die;
    while (<INFO>) {
      if ($_ =~ /ipwr/) {
             $pline = $_;
      }elsif ($_ !=~ /unknown/) {
             print "$pline";
             print "$_";
      }
    }
    close INFO;

open my $fh, "<", "temp.txt" or die "Could not open temp.txt: $!\n";

my $previous_line = "";
while ( my $current_line = <$fh> ) {
    if ( $previous_line =~ /ipwr/ and $current_line !~ /unknown/ ) {
        print "$previous_line $current_line";
    }
    $previous_line = $current_line;
}
close $fh;

    open (INFO, "<temp.txt") or die;
    while (<INFO>) {
      if ($_ =~ /ipwr/) {
             $pline = $_;
      }elsif ($_ !~ /unknown/) {
             print "$pline";
             print "$_";
      }
    }
    close INFO;

open (INFO, "<temp.txt") or die;
open (INFO, "temp.txt") or die;