In all these calls, the U32 wn parameters are warning category constants. You can see the ones currently available in "Category Hierarchy" in warnings, just capitalize all letters in the names and prefix them by WARN_. So, for example, the category void used in a perl program becomes WARN_VOID when used in XS code and passed to one of the calls below.
U32 wn
WARN_
void
WARN_VOID
Should any of the categories by default be enabled even if not within the scope of use warnings, instead use the "ckWARN_d" macros.
use warnings
"ckWARN_d"
The categories must be completely independent, one may not be subclassed from the other.
Like "ckWARN", but for use if and only if the warning category(ies) is by default enabled even if not within the scope of use warnings.
"ckWARN"
These macros are used to pack warning categories into a single U32 to pass to macros and functions that take a warning category parameter. The number of categories to pack is given by the name, with a corresponding number of category parameters passed.
To install utf8, copy and paste the appropriate command in to your terminal.
cpanm
cpanm utf8
CPAN shell
perl -MCPAN -e shell install utf8
For more information on module installation, please visit the detailed CPAN module installation guide.