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From: Ronny on 6 May 2008 06:25 By chance I found out that no error is issued on the following program: perl -w -e 'use strict; print(Does::Not::Exist,"\n")' Instead, "Does::Not::Exist" is printed. Shouldn't there be a warning about the improper use of a bareword? Similarily, the program perl -w -e 'use strict; system(Does::Not::Exist,"\n")' results in the message Can't exec "Does::Not::Exist": No such file or directory at -e line 1. which too seems to suggest that Does::Not::Exist is simply interpreted as string. But when I use it like this: perl -w -e 'use strict; print(ref(Does::Not::Exist),"\n")' I get the more reasonable: Bareword "Does::Not::Exist" not allowed while "strict subs" in use at - e line 1. Why is this bareword treated differently in these contexts? Ronald
From: Ben Bullock on 6 May 2008 23:31 Ronny <ro.naldfi.scher(a)gmail.com> wrote: > By chance I found out that no error is issued on the following > program: > > perl -w -e 'use strict; print(Does::Not::Exist,"\n")' > > Instead, "Does::Not::Exist" is printed. Shouldn't there be a warning > about > the improper use of a bareword? It seems to be a bug in Perl.
From: sheinrich on 7 May 2008 05:51 On May 7, 6:31 am, benkasminbull...(a)gmail.com (Ben Bullock) wrote: > Ronny <ro.naldfi.sc...(a)gmail.com> wrote: > > By chance I found out that no error is issued on the following > > program: > > > perl -w -e 'use strict; print(Does::Not::Exist,"\n")' > > > Instead, "Does::Not::Exist" is printed. Shouldn't there be a warning > > about > > the improper use of a bareword? > > It seems to be a bug in Perl. Even stranger: scripts>perl -we "use strict; print(Does::Not::Exist);" Name "Does::Not::Exist" used only once: possible typo at -e line 1. print() on unopened filehandle Exist at -e line 1. scripts>
From: A. Sinan Unur on 7 May 2008 06:45 sheinrich(a)my-deja.com wrote in news:764d756d-1678-422e-b813-7b39dedc0e3b(a)34g2000hsh.googlegroups.com: > On May 7, 6:31 am, benkasminbull...(a)gmail.com (Ben Bullock) wrote: >> Ronny <ro.naldfi.sc...(a)gmail.com> wrote: >> > By chance I found out that no error is issued on the following >> > program: >> >> > perl -w -e 'use strict; print(Does::Not::Exist,"\n")' >> >> > Instead, "Does::Not::Exist" is printed. Shouldn't there be a >> > warning about >> > the improper use of a bareword? >> >> It seems to be a bug in Perl. > > Even stranger: > > scripts>perl -we "use strict; print(Does::Not::Exist);" > Name "Does::Not::Exist" used only once: possible typo at -e line 1. > print() on unopened filehandle Exist at -e line 1. Note that the issue only arises with print. In the case above, Does::Not::Exist is being taken to refer to a bareword filehandle Exist in the package Does::Not. It then seems like print wants to print $_ to this filehandle. As such, this treatment *may* be consistent with the following excerpt from perldoc perldata: Barewords A word that has no other interpretation in the grammar will be treated as if it were a quoted string. These are known as "barewords". In the case of print Does::Not::Exist; there does seem to be a valid interpretation of Does::Not::Exist as a filehandle if one assumes that $_ is printed. That interpretation is borne out by the following script: #!/usr/bin/perl use strict; use warnings; print STDERR while $_ = shift; __END__ Now, let's go back to print Does::Not::Exist, "\n"; The comma between Does::Not::Exist and "\n" tells print that Does::Not::Exist is not a filehandle. Note the following cases: C:\t> perl -w -Mstrict -e "print Does,Not,Exist, qq{\n}" No comma allowed after filehandle at -e line 1. In this case, Does has a valid interpretation as a bareword filehandle. Thus, strict does not kick in. C:\t> perl -w -Mstrict -e "print Does'Not'Exist, qq{\n}" Does::Not::Exist Note that ' and :: are equivalent, AFAIK. C:\t> perl -w -Mstrict -e "print Does-Not-Exist, qq{\n}" Bareword "Exist" not allowed while "strict subs" in use at -e line 1. Execution of -e aborted due to compilation errors. Note no complaint about Does and Not. I don't know why. C:\t> perl -w -Mstrict -e "print Does+Not+Exist, qq{\n}" Bareword "Not" not allowed while "strict subs" in use at -e line 1. Bareword "Exist" not allowed while "strict subs" in use at -e line 1. Execution of -e aborted due to compilation errors. Note no complaint about Does. I don't know why. Again, let's go back to: C:\t> perl -w -Mstrict -e "print Does::Not::Exist, qq{\n}" Does::Not::Exist The comma establishes that Does::Not::Exist is not referring to filehandle Exist in the package Does::Not. Recall the excerpt from perldata above. Is there a valid interpretation of Does::Not::Exist in the current grammar? I claim that there is. The :: characters in the name establish that it is the name of a package. So, it is printed. Sinan -- A. Sinan Unur <1usa(a)llenroc.ude.invalid> (remove .invalid and reverse each component for email address) comp.lang.perl.misc guidelines on the WWW: http://www.rehabitation.com/clpmisc/
From: sheinrich on 7 May 2008 09:47 On May 7, 1:45 pm, "A. Sinan Unur" <1...(a)llenroc.ude.invalid> wrote: .... > Note the following cases: > > C:\t> perl -w -Mstrict -e "print Does,Not,Exist, qq{\n}" > No comma allowed after filehandle at -e line 1. > > In this case, Does has a valid interpretation as a > bareword filehandle. Thus, strict does not kick in. > But why is the first argument being taken here for a filehandle, in spite of the comma, and not considered as namespace, as in your other example? .... > > Again, let's go back to: > > C:\t> perl -w -Mstrict -e "print Does::Not::Exist, qq{\n}" > Does::Not::Exist > > The comma establishes that Does::Not::Exist is not referring to > filehandle Exist in the package Does::Not. > It seems like only Strings containing :: (or ' ) qualify as possible package names. Steffen
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