What are the permissions on the directory that contains your script. Try this script in the same directory as your script to check the directory is writable to by your webserver

#!/usr/bin/perl
# testwrite.pl
use strict;
use Cwd;
print "Content-type: text/plain\n\n";

my $cwd = cwd();
if ( open my $fh,'>',$cwd.'/testwrite' ){
  print "OK $cwd is writable"
} else {
  print "ERROR $cwd is NOT writable"
}
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