Examine the code in your Fcntl.pm file. Mine contains: 
# Named groups of exports
%EXPORT_TAGS = (
    'flock'   => [qw(LOCK_SH LOCK_EX LOCK_NB LOCK_UN)],
 ...

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Possibly this tag was not defined in the version of Fcntl.pm that came with Perl 5.6.0. You could get around this various ways, such as by importing the listed symbols directly or by updating the Fcntl module.

In reply to Re^3: "flock" is not defined in %Fcntl::EXPORT_TAGS at /usr/lib/perl5/Exporter.pm by tall_man
in thread "flock" is not defined in %Fcntl::EXPORT_TAGS at /usr/lib/perl5/Exporter.pm by vivia

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