Beefy Boxes and Bandwidth Generously Provided by pair Networks
Don't ask to ask, just ask

Why dosen't => quote barewords with ::?

by MrNobo1024 (Hermit)
on Aug 08, 2002 at 23:21 UTC ( #188782=perlquestion: print w/replies, xml ) Need Help??
MrNobo1024 has asked for the wisdom of the Perl Monks concerning the following question:

This one-liner
perl -e 'use strict; my %foo = (Bar::Baz => "qux")'
produces the error
Bareword "Bar::Baz" not allowed while "strict subs" in use at -e line +1. Execution of -e aborted due to compilation errors.
I thought => was supposed to quote barewords? Has the behaviour of this changed since 5.6? There are a few modules that do something like
use strict; use Attribute::Handlers autotie => { __CALLER__::Attribute => __PACKAG +E__ };
and I had to quote __CALLER__::Attribute to get it to work on 5.8.


Replies are listed 'Best First'.
Re: Why dosen't => quote barewords with ::?
by Abigail-II (Bishop) on Aug 09, 2002 at 09:17 UTC
    It's a bug. It works ok in 5.6.1. From perldata:
    It is often more readable to use the "=>" operator between key/value pairs. The "=>" operator is mostly just a more visually distinctive synonym for a comma, but it also arranges for its left-hand operand to be interpreted as a string--if it's a bareword that would be a legal identi- fier.
    Bar::Baz is a valid identifier.

    I'll perlbug it.


Re: Why dosen't => quote barewords with ::?
by kvale (Monsignor) on Aug 08, 2002 at 23:29 UTC
    From the 5.8.0 docs:
    The => digraph is mostly just a synonym for the comma operator. It's useful fordocumenting arguments that come in pairs. As of release 5.001, it also forces any word to the left of it to be interpreted as a string.
    It appears that 5.8.0's idea of a word does not include colons.


Re: Why dosen't => quote barewords with ::?
by Zaxo (Archbishop) on Aug 08, 2002 at 23:59 UTC

    Stringy comma's idea of a word is the same as \w+ in a regex, /^[0-9A-Z_a-z]+$/.

    Update: fixed typo, ++tadman for spotting it.

    After Compline,

      Actually id say that that regex is not quite right. First of all this comes down to the defintion of a bareword, which isnt well defined from what ive read. But if we must discuss a regex for this purpose I would say it would be more like the following, but even then its not _entirely_ clear (the issue of v strings rears its head as well as a few other issues)
      (Im debating the \s* bit. Ive put it in becuase of Juerds comment below, but on reflection I dont actually think its necessary as the tokenizer would be remove the whitespace the surrounds the token preceeding the => digraph before the parser even saw the digraph.)

      To be honest IMO there isnt an exact regex. The rules of the tokenizer are not representable by a regex as far as I know. (I could be wrong, it happens a lot. :-)

      Some bizarre examples:

      use strict; use warnings; local $\="\n"; local $,="\t"; print Zaxo => 'Juerd'; print Zax0 => Ju3rd => 'Foo'; print -abcde=>'foo'; print v9. => v65; print 0 => 'foo'; print v48.65 => 'A0'; print 0x00 => 'foo'; #prints 0 not 0x00 # print 1a2b => 'foo'; #doesnt work, cant have alphas when the key sta +rts with a digit (0x excepted) # print 1a-2b => 'foo'; #doesnt do what you might think, evals to 0
      Anyway, if you are interested in this , there is currently a discussion on p5p about the behaviour of => (started by Abigail-II) called
      [perl #16010] v-strings left of a => don't get quoted.
      It seems the issues of => and v strings are quite convoluted. :-)

      Yves / DeMerphq
      Software Engineering is Programming when you can't. -- E. W. Dijkstra (RIP)


       /^[0-9A-Z_a-z]+\z/, because $ matches before \n if present. \z is end of string.

      - Yes, I reinvent wheels.
      - Spam: Visit eurotraQ.

Log In?

What's my password?
Create A New User
Node Status?
node history
Node Type: perlquestion [id://188782]
Approved by kvale
and all is quiet...

How do I use this? | Other CB clients
Other Users?
Others chilling in the Monastery: (6)
As of 2018-05-24 22:30 GMT
Find Nodes?
    Voting Booth?