This is how i would do that:

use strict;
use warnings;
use File::Temp qw( tempdir );
use Test::More tests => 2;

my $fname = 'foo.txt';
my $dir   = tempdir( CLEANUP => 1 );

is -f "$dir/$fname", undef, "file does not exit";

create_file( $dir, $fname );

is -f "$dir/$fname", 1, "file now exists";

sub create_file {
    my ($path, $fname) = @_;
    open FH, '>', "$path/$fname" or die "$!\n";
    close FH;
}
[download]

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)