Since you mentioned that you're new to Perl and programming in general, let me explain this line by line. I've been working introductory tutorials for work, so I figure this is good practice. My apologies if you already know some of these.

use strict;
use warnings;
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These two lines are called "pragmas" and make your program less tolerant of sloppy code. You should start every Perl program with these two lines.

use FileHandle;
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Use the built-in FileHandle module, which allows you to treat file handles (variables in the program that represent files) as objects (a programming construct that allows you to treat a variable as a self-contained entity with properties and "things it can do", also called methods).

for (my $i = 0; $i < @myArr; $i++) {
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Create a new variable called $i, make it equal to 0. Repeat the following section (the section down to the matching '}') as long as the value of $i is less than the number of elements in the @myArr array. After finishing each loop, increment $i and do the test again.

# set $value to the value held in the array position we're on
my $value = $myArr[$i]; 
# set $index to one more than our current array position
my $index = $i + 1; 
#create our filename - when i = 0, it will be "file1"
my $file = "file${index}"; 
write_value_to_file($value, $file); 
# call our function below with our current value and filename
} 
# end the for block
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Now we'll look at the function (or subroutine) write_value_to_file:

#we're starting a new subroutine
sub write_value_to_file {   
# set two variables from the values given to this function   
my ($value, $fname) = @_; 
#create a new FileHandle object  
my $fh = new FileHandle;  
# open the file name in $fname for writing, and refer to it by $fh
open ($fh, ">", $fname)   
# if opening the file failed, tell the user why and exit
  or die "unabel to write $fname($!)\N"  
#write the value, followed by a newline character, to the file
print $fh "$val\n"l   
# tell the program we're done with this file.
close $fh;     
#close the function
}
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Hopefully this was at least a little helpful.

UPDATED: mention $i++. Thanks johngg!