Add $! into your print and it will show you reason for failure.

unless (cpen (FH, $myhashname)) {
print STDERR "Can not open file\"$myhashname\": $!n\n";
exit;}
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BTW much more common ideom for doing same thing (opening file and exiting with error in case of failure) is:

open (FH, $myhashname)
    or die "Can not open file\"$myhashname\": $!";
[download]

--
Ilya Martynov (http://martynov.org/)