=over =item $PREMATCH =item $` X<$`> X<$PREMATCH> The string preceding whatever was matched by the last successful pattern match (not counting any matches hidden within a BLOCK or eval enclosed by the current BLOCK). (Mnemonic: C<`> often precedes a quoted 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. See L for a replacement. =back