You have a rather restrictive set of requirements. The implicit loop, using these other options like "naF" as well using an END block as you described aren't usually seen.

I guess it is possible that this is some homework assignment. If it is, then I think this is not a very good one because it uses some features that just aren't used that often.

A more typical thing would be like shown below. There would be some way to get a "usage statement" if the input command was wrong. The input/output "opens" would be done near the beginning of the program. You don't want to have a program that runs a long time, then bombs because the output permissions or path to the output file means that no result can be output!

If you want to process multiple files, I show a simple foreach loop below that will do that. There is no need to close a filehandle before you open it to another file.

Below I show "my @result" just needs to be declared at a higher scope that the input loop. An "our" variable is usually used for situations where a variable needs visibility outside the package it was defined in, which is not the case here.

Anyway, if your requirement statements aren't driven by a homework assignment, I would do something a lot more straightforward.

#! usr/bin/perl -w
use strict;

if (@ARGV == 0)
{   
   print "usage: perl test.pl infile [infile]\n";
   exit(1);
}   

my $outfile = "outfile.txt";
open (OUTFILE, '>', $outfile) or 
               die "unable to open $outfile : $!\n";

my @result;

foreach my $infile (@ARGV)
{
    open (INFILE, '<', $infile) or 
                   die "unable to open $infile : $!\n";
    while (<INFILE>)    
    {                 
        chomp;
        my (@vars) = split(/;/,$_);
        push @result, "@vars";
        print "Processed $infile line no.: $. vars= @vars\n";
    }
}

print "Result Array contains: " . @result . " element(s).\n";
writeToFile( \@result);

sub writeToFile 
{
   my $array_ref = shift;
   foreach ( @{ $array_ref } ) 
   {
       print OUTFILE "$_\n";
   }
}
 
__END__
infile.txt:
1;2;3
a;b;c
4;5;6

infile2.txt:
X;Y;Z
9;10;11

C:\TEMP>perl newbie3.pl infile.txt infile2.txt
Processed infile.txt line no.: 1 vars= 1 2 3
Processed infile.txt line no.: 2 vars= a b c
Processed infile.txt line no.: 3 vars= 4 5 6
Processed infile2.txt line no.: 4 vars= X Y Z
Processed infile2.txt line no.: 5 vars= 9 10 11
Result Array contains: 5 element(s).

C:\TEMP>cat outfile.txt
1 2 3
a b c
4 5 6
X Y Z
9 10 11
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