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Postings from August 2009
2009/8/27 Abigail <abigail@abigail.be>: > On Thu, Aug 27, 2009 at 09:33:13AM +0100, Zefram wrote: >> chip@seas.upenn.edu (via RT) wrote: >> >$ perl -p -e 's_/32__;' >> >> The underscore is not perceived as a delimiter there, but as part of >> an identifier. Observe how it was parsed: >> >> $ perl -MO=Deparse -e 's#/32##;' >> s[/32][]; >> -e syntax OK >> $ perl -MO=Deparse -e 's_/32__;' >> 's_' / 32; >> -e syntax OK >> >> Other clues are available if you turn on warnings: >> >> $ perl -wce 's_/32__;' >> Misplaced _ in number at -e line 1. >> Misplaced _ in number at -e line 1. >> Useless use of division (/) in void context at -e line 1. >> -e syntax OK >> >> And if the substitution had contained other text then it would have >> blown up earlier: >> >> $ perl -wce 's_\\__;' >> Backslash found where operator expected at -e line 1, near "s_\" >> syntax error at -e line 1, near "s_\" >> -e had compilation errors. >> >> I believe the documentation is at fault. perlop(1) says: >> >> Any non-alphanumeric, non-whitespace delimiter may replace the >> slashes. >> >> Underscore is not alphanumeric or whitespace, but is evidently >> being treated the same way that an alphanumeric character would be. >> The prohibition is really on identifier characters, not alphanumerics. The doocumentation should read "non-perl-word, non whitespace delimiter" We use "alphhanumeric" fairly regularly when we speak of "perl-word-characters" or "identifier" (which cannot be expressed by a character class as it cannot start with a number, yet can end with one). > > > But even then, the documentation isn't correct. You *can* use word characters > as delimiters: > > s _/32__ > > and > > s s/32ss > > are fine. > > The problem here lies in the tokenization part: the first token of > C<< s_/32__ >> is C<< s_ >>, which isn't the substitution operator. > > In fact, this issue isn't any different from saying you cannot use C<< _ >> > as a function argument because you wrote: > > C<< func_ >> > > which isn't parsed as C<< func (_) >> either. Right. This is not a bug. Cheers, Yves -- perl -Mre=debug -e "/just|another|perl|hacker/"Thread Previous | Thread Next