=over =item $PERLDB =item $^P X<$^P> X<$PERLDB> The internal variable for debugging support. The meanings of the various bits are subject to change, but currently indicate: =over 6 =item 0x01 Debug subroutine enter/exit. =item 0x02 Line-by-line debugging. Causes C subroutine to be called for each statement executed. Also causes saving source code lines (like 0x400). =item 0x04 Switch off optimizations. =item 0x08 Preserve more data for future interactive inspections. =item 0x10 Keep info about source lines on which a subroutine is defined. =item 0x20 Start with single-step on. =item 0x40 Use subroutine address instead of name when reporting. =item 0x80 Report C as well. =item 0x100 Provide informative "file" names for evals based on the place they were compiled. =item 0x200 Provide informative names to anonymous subroutines based on the place they were compiled. =item 0x400 Save source code lines into C<@{"_<$filename"}>. =item 0x800 When saving source, include evals that generate no subroutines. =item 0x1000 When saving source, include source that did not compile. =back Some bits may be relevant at compile-time only, some at run-time only. This is a new mechanism and the details may change. See also L. =back