my @list;
#Read first, ask questions later is probably not optimal for this
#Scope our variable, merge, read, and assign all at once
while(chomp(my $line = <NETLIST>)){
  #Save a match, substitution returns true iff we susbtituted
  if ($line =~ s/^\+//){
    #Append to previous line (last line in the array)
    $list[-1] .= $line;
  }
  else{
    #Save the line
    push(@list, $line);
  }
}
#Map is good, nice way to get all the newlines back
#join would work if you the file need not end in a newline
print map {"$_\n"} @list;