Solution:

As indicated previously in this thread the culprit was DBI.
After the DBI->connect statement the decimalpoint was changed to decimalcomma, though that's not entirely true as decimal comma was not allowed in the perlcode.

I have solved this by resetting the LC_NUMERIC parameter directly after the connect command

use POSIX qw(locale_h);
.
.
my $dbh = DBI->connect("DBI:ODBC:$dsn") or die "Could not connect to $
+dsn\n";
setlocale(LC_NUMERIC, "C");
.
.
[download]

Just hoping that I won't be bitten in the back by some other aspect of locales ;-/
Anyway thanks all for your support and Hey I got to know Devel::Peek and locales along the journey!
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I would like to change the world but God won't let me have the source code.