Here is an example

#!/usr/local/bin/perl
my $outfile = shift; # You have to use shift here for magic to work
open (OUT, ">$outfile") || die $!;
while (<>){ # This is magic, it opens all the files that are on @ARGV
    print OUT $_;
}
close (OUT);
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What if you would have the files been selected from a select menu. Like one dropdown with one file name and another with the other file name using a form to submit the information and display results to the browser window?

That is different, but it isn't too hard...first, you need to use CGI.pm, then you get a list of the files, open them and write them out to another file. Here is an example...your webform will need one input named 'outfile' for the file you want to save to. You will also need a series of inputs named 'fileX' where 'X' is a number, one for each input file.

WARNING!!! This example doesn't use taint in order to make it more readable. In a real script you should always use taint.

use CGI;

my $q = new CGI; # Get a CGI object
open (OUT, ">$q->param('outfile')") || die $!; # Open our output file
my @files = grep{/^file\d+$/} $q->param(); # Grab a list of params
for my $filename (@files){
    open (IN, $q->param($filename)) || die $!; # Open each input file
    print OUT <IN>; # Print the input file to the output file
    close (IN); # Make sure you close the input file
}
close (OUT);
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