Just to be on the safe side, I'd advice you to habitually use the strictures ,this is like the ABS system in a car and can really stabilize you from slipping into errors or typos: 
use strict;
use warnings;

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Another advice is to use the three argument form of open and show the open modes your files are accessed under (input, output, appending, piping...), 

open (FH, '<', "saved_system.txt");

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A third advice with open is to provide for explanation/clues of errors that could ensue, like if the file couldn't be opened, didn't exist, didn't have access attributes and more importantly if system-errors where involved, these clues can be indicated from $!.. 
open(FH, '<', 'saved_system.txt')or die("Couldn't open file, $!");

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to read the perlvar documentation for $! from the terminal prompt of your machine, "perldoc perlvar $!"

Update:ikegami posted a wholesome example while I was writing these ideas :)...

Excellence is an Endeavor of Persistence. Chance Favors a Prepared Mind.

In reply to Re: comparing lines in two files by biohisham
in thread comparing lines in two files by Baphi

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