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Re: Parens mess up regex substitute

by davido (Archbishop)
on Jan 26, 2012 at 06:43 UTC ( #950030=note: print w/replies, xml ) Need Help??


in reply to Parens mess up regex substitute

perlop:

PATTERN may contain variables, which will be interpolated every time the pattern search is evaluated, except for when the delimiter is a single quote.

Parens aren't the only thing you have to look out for. '.' (dot) will be treated as a meta-character that matches anything except for newline. [] square brackets will be treated like character classes, and so on through the entire list of regexp pattern tokens. quotemeta or \Q and \E are not just quirks providing a lucky solution, this sort of situation is on the short list of reasons for quotemeta and \Q\E to exist.

In perldoc -f quotemeta you'll read, "quotemeta (and \Q ... \E ) are useful when interpolating strings into regular expressions, because by default an interpolated variable will be considered a mini-regular expression. I wouldn't call it an anomaly, it's just how Perl is designed.

perlop contains a good crash course on how interpolation works. The sections to look for start with Quote and Quote-like Operators, and continue through the end of "Gory details of parsing quoted constructs".


Dave

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[GotToBTru]: so I emailed my contact asking if we could just stop sending it .. I'm afraid she is going to ask "what is that anyway?"
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[MidLifeXis]: Most likely it is a code that some undocumented system, hidden behind layers of IT, deep in the bowels of the building under the machine room floor, reads that code to keep a presence switch from going off. :-b
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