Why would you want to replace undef values (which correspond to NULL-values in the database) with the string "null" anyway? That can change the datatype of the column (since numeric columns can also contain NULL values, which you change to a text datatype).

To answer your question, if you use 

$sth->bind_columns(\$var1, \$var2, \$var3);

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You'd have to check all vars to see if they're undef after fetching data and act accordingly.
This method might make things simpler: 
@list_of_refs_to_vars_to_bind = (\$var1, \$var2, \$var3);
$sth->bind_columns(@list_of_refs_to_vars_to_bind);

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Now you can use 
map { $$_ = "null" if (!defined $$_); } @list_of_refs_to_vars_to_bind;

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to do your evil thing.

In reply to Re: check bind_columns for undefined values by Neighbour
in thread check bind_columns for undefined values by gropey

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