Untested code follows. It's highly inefficient, but you get the idea:

my (@first, @second);

{

    local *FILE1;

    local *FILE2;

    open(FILE1, $file1) || die "Can't open $file1: $!";

    open(FILE2, $file2) || die "Can't open $file2: $!";

    @first = reverse split(//, <FILE1>);

    @second = reverse split(//, <FILE2>);

    close FILE1;

    close FILE2;

}



while (@first) {

    my $couplet = shift @first . shift @second;

    print "$couplet ";

}
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A more efficient technique would involve substr and not that yucky reverse split magic, which may not work anyway. (I'm not at a machine where I can test this right now.)

Update: chop is a better solution yet.