You'll need to use globals or closures:

# From almut
sub make_wanted {
    my $arg = shift;
    return sub {
        my $diskpathfile = $File::Find::name;
        print "$arg: $diskpathfile\n";
    }
}

my $arg = "hello";
find(make_wanted($arg), $source);
[download]

or

sub wanted {
    my ($arg) = @_;
    my $diskpathfile = $File::Find::name;
    print "$arg: $diskpathfile\n";
}

my $arg = "hello";
find(sub { wanted($arg) }, $source);
[download]

or

my $arg = "hello";
find(sub {
    my $diskpathfile = $File::Find::name;
    print "$arg: $diskpathfile\n";
}, $source);
[download]

or

my $arg = "hello";

sub wanted {
    my $diskpathfile = $File::Find::name;
    print "$arg: $diskpathfile\n";
}

find(\&wanted, $source);
[download]