my @output = `bpdbjobs`;
#while (<DATA>){
for (@output) {
  # process lines
}

##</code><code>##

my $filename  = 'output.txt';
open my $fh,'<',$filename or die "Could not open $filename : $!";
while (<$fh>){
  # process lines
}

##</code><code>##

open my $fh, '-|', 'bpdbjobs' or die $!;
while (<$fh>){
  # process lines
}
close $fh or die $! ? $! : $?;