Most likely because cacheout, whatever that is, returns undef instead an opened filehandle. Check that:

die "Didn't get a sensible result from cacheout() for '$file'. Maybe t
+his helps: $!"
    unless $fh;
[download]

Looking closer at your error message and the increasing number of filehandles, it seems that cacheout() returns a fileno and not something that Perl considers a valid, open filehandle. The error is likely in cacheout().

Looking closer at your topic I now realize you're talking about FileCache, stupid me.

Looking even closer, I can't replicate your problem:

Q:\>type test.txt
1
2
3

Q:\>perl -MFileCache -le "my $fh = cacheout('<','test.txt'); print for
+ <$fh>"
1

2

3

Q:\>perl -MFileCache -le "my $fh = cacheout('<','does-not-exist.txt');
+ print for
 <$fh>"
Can't create does-not-exist.txt: No such file or directory at -e line 
+1
[download]

So maybe the file exists but you don't have read permissions? This is on Win32, Perl 5.8.2, stock FileCache