and dynamically scoped to the current BLOCK.
The use of this variable anywhere in a program imposes a considerable
-performance penalty on all regular expression matches. See L<BUGS>.
+performance penalty on all regular expression matches. See L</BUGS>.
=item $PREMATCH
string.) This variable is read-only.
The use of this variable anywhere in a program imposes a considerable
-performance penalty on all regular expression matches. See L<BUGS>.
+performance penalty on all regular expression matches. See L</BUGS>.
=item $POSTMATCH
This variable is read-only and dynamically scoped to the current BLOCK.
The use of this variable anywhere in a program imposes a considerable
-performance penalty on all regular expression matches. See L<BUGS>.
+performance penalty on all regular expression matches. See L</BUGS>.
=item $LAST_PAREN_MATCH
is identical to C<$Config{'osname'}>. See also L<Config> and the
B<-V> command-line switch documented in L<perlrun>.
+=item ${^OPEN}
+
+An internal variable used by PerlIO. A string in two parts, separated
+by a C<\0> byte, the first part is the input disciplines, the second
+part is the output disciplines.
+
=item $PERLDB
=item $^P