in reply to quoting style for lists

If I'm not completely misled: The => operator causes it's left operand to be seen as string as long as it only contains \w-characters and perhaps a leading -minus. The same rules afaik apply for $hash{keys}. In any other position you will get a bareword error from strict, which is in use anyway ;)

print Hello => ", $name\n";
%hair = ( Peter => 'green', Charles => white => ucfirst('mary') => 're
+d' );
print "your hair is ",$hair{$name},"\n",
     "Peter's hair is ",$hair{Peter},"\n";

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Re: quoting style for lists
by Abigail-II (Bishop) on Aug 01, 2002 at 17:26 UTC
    The => operator causes it's left operand to be seen as string as long as it only contains \w-characters and perhaps a leading -minus. The same rules afaik apply for $hash{keys}. In any other position you will get a bareword error from strict, which is in use anyway ;)
    Well, it's a bit more complicated. Watch: 
    #!/bin/sh

for word in 'foo' '-foo' 'foo::bar' '-foo::bar' 'FOO'
do  code='$_ = '$word'; print'
    for  args in ' ' '-w' '-Mstrict' '-Mstrict -w'
    do   cmd="perl $args -le '$code'"
         echo $cmd
         eval $cmd
         echo
    done
done

    [download]
    Running this gives: 
    perl -le '$_ = foo; print'
foo

perl -w -le '$_ = foo; print' 
Unquoted string "foo" may clash with future reserved word at -e line 1.
foo
         
perl -Mstrict -le '$_ = foo; print'
Bareword "foo" not allowed while "strict subs" in use at -e line 1.
Execution of -e aborted due to compilation errors.

perl -Mstrict -w -le '$_ = foo; print'
Bareword "foo" not allowed while "strict subs" in use at -e line 1.
Execution of -e aborted due to compilation errors.
 
perl -le '$_ = -foo; print'
-foo
 
perl -w -le '$_ = -foo; print'
-foo
 
perl -Mstrict -le '$_ = -foo; print'
-foo

perl -Mstrict -w -le '$_ = -foo; print'
-foo
         
perl -le '$_ = foo::bar; print'
foo::bar

perl -w -le '$_ = foo::bar; print'
foo::bar

perl -Mstrict -le '$_ = foo::bar; print'
Bareword "foo::bar" not allowed while "strict subs" in use at -e line 1.
Execution of -e aborted due to compilation errors.

perl -Mstrict -w -le '$_ = foo::bar; print'
Bareword "foo::bar" not allowed while "strict subs" in use at -e line 1.
Execution of -e aborted due to compilation errors.
 
perl -le '$_ = -foo::bar; print'
-foo::bar

perl -w -le '$_ = -foo::bar; print'
-foo::bar
         
perl -Mstrict -le '$_ = -foo::bar; print'
-foo::bar

perl -Mstrict -w -le '$_ = -foo::bar; print'
-foo::bar

perl -le '$_ = FOO; print'
FOO

perl -w -le '$_ = FOO; print'
FOO

perl -Mstrict -le '$_ = FOO; print'
Bareword "FOO" not allowed while "strict subs" in use at -e line 1.
Execution of -e aborted due to compilation errors.

perl -Mstrict -w -le '$_ = FOO; print'
Bareword "FOO" not allowed while "strict subs" in use at -e line 1.
Execution of -e aborted due to compilation errors.
    Interesting, isn't? (And yes, there are good reasons why Perl behaves this way - I won't tell you know, think about it for a while)

    Abigail

[reply]
[d/l]

      I see, what use should any unary '-' with bareword have apart from being a shell-option-like string? Thanks.
      But even the use of -barewords at other positions than before => and inside $hash{keys} is hairy anyway: 

      use strict; use warnings;

sub foo(){ 'x' }

$_ = -foo; # Ambiguous use of -foo 
           # resolved as -&foo() at ./ol line 8.

print; # '-x'

sub bar() { -1 }
$_ = -bar; #Ambigous ... as -&bar() ...
print; # 1 !not "--1"

my %h = ( -foo => 'FOO' );
print keys %h,' : ',$h{-foo}; # '-foo : FOO'

      [download]

      So to be on the safe side one should quote at these points, because if there is a reserved word 'foo' in the future, you will have a problem writing -foo barely.

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[reply]
[d/l]
            sub bar() { -1 }
    $_ = -bar; #Ambigous ... as -&bar() ...
    print; # 1 !not "--1"

        [download]
        Documented! From man perlop: 
               Unary "-" performs arithmetic negation if the operand is
       numeric.  If the operand is an identifier, a string con-
       sisting of a minus sign concatenated with the identifier
       is returned.  Otherwise, if the string starts with a plus
       or minus, a string starting with the opposite sign is
       returned.  One effect of these rules is that "-bareword"
       is equivalent to "-bareword".
        For fun, let "bar" return qq {-1}, and see one of the places in Perl were it matters whether a value is a string or a number.

        Abigail

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