Opening a file is slow anyway, and the additional error check doesn't cost you anything. And having Perl telling you the reason why it cannot create a file instead of the file silently not being created (or updated) is priceless. So, always check your open() calls for failure and output the error message together with the filename.

Lets assume you have a program that takes one hour to run:

somefunction() # takes 1 second to run
foreach ( @bigmightarrayof360000 ) {
  someotherfunction($_); #takes 0,01 seconds to run
}
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Now if you could throw away some error checking code in somefunction() to have its runtime down to 0,5 seconds, would you do it? Your program would gain an unnoticable speedup and in case of error either silently fail or even produce inconsistent data

There are a few golden rules in optimization:

* Don't optimize when you don't need to, i.e. if the program runs fast enough, don't optimize

* Don't optimize prematurely

* Don't optimize where it doesn't count. Usually say 5% of the code is responsible for 95% of the runtime. If you optimize in the other 95% of the code, you wasted your time for minimal gain

* Optimization is a trade off. You might gain speed, but most of the time you lose on readability, memory usage, maintainability or safety. So be sure you can afford the loss.

You might also like to read the section 'When to optimize' in Optimization_(computer_science)

Doesn't this take more work (ie for perl, longer runtime)?

my @file_info = stat($output_file)
   or die "$output_file: stat failed: $!\n";
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My code was well-formatted ;o) In case you want to use or copy code examples, please use the download link which should be shown below the code area. (I had to learn this lesson as well ;o))

If your open fails, the corresponding filehandle doesn't work and all following commands, which use that filehandle will run into errors or/and will print warnings (if enabled; which generally should be done).

By checking the success of the open, you can define what to do if it was successful, and what to do if not.

If you want to read from a file:

open my $fh, '<', $not_existent_filename;
while ( my $line = <$fh> ) {
  print $line;
}
close $fh;
print "END OF READ\n";
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If warnings are enabled, you'll get a warning about "readline() on closed filehandle", but you cannot distinguish between this failure and an empty file.

If you recognize a delay by one single "or die ..." (or by the three I had in my previous example) in your script execution, I'm very impressed ;o)

Are there more efficient programming languages that I should be aware of?

Javafans answer was a bit sarcastic because it doesn't really make sense to ask about efficiency around an open (which is maybe a thousand times slower than the following test you are worried about.

There are faster languages about, for example C/C++ and assembly language. But that doesn't mean that YOU are faster in programming them. Or that it is as much fun programming in them. Tasks that are done in perl with a few lines need sometimes hundreds of lines in C. Pray that you have a fitting library at hand.

For example, Hashes are used extensively in modern languages like perl, they are the bred-and-butter data structure and used for 80% of all data storage in a program. In C/C++ you can either:
a) use a self-made data structure perfectly fitting the job, you only need 5 days instead of 1 to write the program and it might be noticably faster or not.
b)use a hash library to get nearly the comfort of perl but also the same speed as perl for the handling of the data structure

Don't get me wrong, if speed is all you care about, then use C/C++. If you need to write programs that have to make full use of every single memory bit and processor cycle of your machine, use C/C++. If you need to write low level hardware driver stuff, use C/C++. If you want to write programs faster, securer, testable, have better debugging, with more ease, have more libraries to choose from, want to use hashes and regex and other modern features extensively, want to program for the web or other high-level areas (i.e. far form the hardware), use perl.

Note that you can combine perl and C-code (with limits) so it is often possible to write perl code and optimize the critical code parts with C code, if run time is critical