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Perl Language Reference Manual
by Larry Wall and others
Paperback (6"x9"), 724 pages
ISBN 9781906966027
RRP £29.95 ($39.95)

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Quantifier unexpected on zero-length expression; marked by <-- HERE in m/%s/

(W regexp) You applied a regular expression quantifier in a place where it makes no sense, such as on a zero-width assertion. Try putting the quantifier inside the assertion instead. For example, the way to match "abc" provided that it is followed by three repetitions of "xyz" is /abc(?=(?:xyz){3})/, not /abc(?=xyz){3}/.

The <-- HERE shows in the regular expression about where the problem was discovered.

ISBN 9781906966027Perl Language Reference ManualSee the print edition