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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.

The use of this variable anywhere in a program imposes a considerable performance penalty on all regular expression matches. To avoid this penalty, you can extract the same substring by using "@-". Starting with Perl v5.10.0, you can use the /p match flag and the ${^PREMATCH} variable to do the same thing for particular match operations.

This variable is read-only and dynamically-scoped.

Mnemonic: ` often precedes a quoted string.