=over =item $^M X<$^M> By default, running out of memory is an untrappable, fatal error. However, if suitably built, Perl can use the contents of C<$^M> as an emergency memory pool after Cing. Suppose that your Perl were compiled with C<-DPERL_EMERGENCY_SBRK> and used Perl's malloc. Then $^M = 'a' x (1 << 16); would allocate a 64K buffer for use in an emergency. See the F file in the Perl distribution for information on how to add custom C compilation flags when compiling perl. To discourage casual use of this advanced feature, there is no L long name for this variable. This variable was added in Perl 5.004. =back