Well, my question boils down to the following few lines, but I suspect that it's a <duck>bug in Perl 5.6</duck> : 
use base qw(Exporter);
*isa = \&UNIVERSAL::isa;
print isa({}, 'HASH');

# Output under perl 5.6     : Undefined subroutine &main::isa called a
+t - line 4.
# Output under perl 5.005_03: 1

[download]
If I comment out the use base line, or change the glob name from isa to anything else, it works fine. Any ideas why this is happening?

In reply to use base qw(Dazed Confused) by MeowChow

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