I'd swear I've asked this question, but since I can't find the post, here's hoping I didn't :)

Basically, deleting subroutines from a symbol table seems a bit buggy, but I don't know if this behavior is documented or not.

#!/usr/bin/perl -l

sub this { 'this' }
print this;
undef &main::this; # undefine the code slot
print main->can('this') ? 'main->can("this")' : '! main->can("this")';
eval {print this};
print $@;
undef *main::this; # undefine the entire glob
print main->can('this') ? 'main->can("this")' : '! main->can("this")';

__END__
# result
this
main->can("this")
Undefined subroutine &main::this called at sub.pl line 7.

! main->can("this")

[download]

The first time I try to remove the subroutine via undef it still leaves a CODE slot in the symbol table's *this glob. I can't just use delete because it's not an array or a hash (it fails if you try). This is bad in procedural code but it's awful in OO code because $object->can('this') will succeed even if the method has been deleted.

This leaves me with having to undefine the entire glob but that's a horrible solution because the other slots in the glob, if any, are blown away. Is this a known/documented bug/feature in Perl? Is there a workaround?

Cheers,
Ovid

New address of my CGI Course.

In reply to Removing subroutines from symbol tables by Ovid

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