I have some code that handles 'variables' in a class's "hash". Various reasons for it, but main that I remember (it's been around for a few years), was to prevent me from accidently putting in 'garbage' in the {} when I accessed a class var. In line with that, the Data::Vars class does various types of complaining, some of which can be silenced, but will complain about trying to access a var not in the class (or initialize a var not in the class), can complain if you already have an accessor for the 'var', can set it up to perform "default initializations", for the vars that get set on any new object, if a ref, can make sure the "type" isn't changed at runtime, by accident (i.e. a warning). among a few other things. They get used a fair amount in much of the code I write. An example from code running against 5.16: 
#!/usr/bin/perl
our @fields;
use mem(@fields=qw(one two three));
use Data::Vars \@fields, {one=>1, two=>2, three=>3};
use P;

my $self=main->new();

P "one=%s, two=%s, three=%s", $self->one, $self->two, $self->three;

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running it produces no big surprises: 
> /tmp/t.pl
one=1, two=2, three=3

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Where my surprise has come is trying to run in under 5.14 on cygwin. I get an immediate error: 
> /tmp/t.pl
Can't modify logical and (&&) in lvalue subroutine return at /Users/la
+w.Bliss/bin/lib/Data/Vars.pm line 108, near "}"
BEGIN not safe after errors--compilation aborted at /Users/law.Bliss/b
+in/lib/Data/Vars.pm line 111.
Compilation failed in require at /tmp/t.pl line 4.
BEGIN failed--compilation aborted at /tmp/t.pl line 4.

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This has me stumped, since the line it is pointing to just has the "}" on the line (it closes a routine I call the 'main workhorse' of the class). Additionally, in that routine, there ARE no uses of '&&'. While the Vars.pm module has other code in it, this work horse routine is relatively short at 44 lines: 
  sub _Var ($$$;$) :lvalue {                  # Wrkhorse code for manu
+fctrd Vars
    my ($p, $vn, $wa) = @{(shift)};           # vn=varname
    my $c = ref $p || $p;
    my $rfv = ref $p->{$vn};                  # rfv=ref(type) of var
    my $addrof;
    if ($wa && $wa eq 'α') { $wa=undef, $addrof=1 }
    my $arg = $_[0];
    if (@_ && !$addrof)  {                    # arg for "setter"
      my $rfa = ref $arg;                     # ref of the arg
      unless ( defined($p->{$vn}) && defined $arg ){  # if both not de
+fined
        $p->{$vn} = $arg }

      elsif ($rfv eq ARRAY) {                 ## if type(var)==ARRAY, 
+1 param
        my ($index, $ap) = (shift, $p->{$vn});
        if ($p->{':pusharray'} or ( !looks_like_number($index) ||
            not( (defined $wa) || @_) )) {
          push @{$p->{$vn}}, ($index);            ## convert to "push"
          return $index }                         ## return pushed val
+ue

        else {
          $p->{$vn}[$index] = $_[0] if @_;
          return $p->{$vn}[$index] if defined $wa } }

      elsif ($rfv eq HASH) {              
        my $subvar = shift;                     ## 1 var w/hash is is 
+a key
        $p->{$vn}{$subvar} = $_[0] if @_;       ## another?  =>assign 
+value
        return $p->{$vn}{$subvar} if defined $wa }
      
      else {
        if ((length $rfv) && $rfv ne $rfa ) {   ## incompat assignment
          warn P "Warning: var type redefined from \"%s\" to \"%s\"",
                  $rfv, $rfa }

        $p->{$vn} = $_[0];                    ## assignment is default
        return $p->{$vn} if defined $wa } }   # how to return results?
+ (below)

    if ($rfv eq ARRAY ) {
      if (defined($wa)) {               # arrays  special
        $wa? @{$p->{$vn}} : $addrof ? \$p->{$vn} : $p->{$vn} } }

    elsif ($rfv eq HASH ) { $p->{$vn} } 
    elsif ($addrof) { return $p->{$vn} }
    else  { return $p->{$vn} }
  } ## endsub (#108)
  
  # "address(ref)-of" function (
  sub _addr_of_($) { (#111 -- basically next line of code)

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The line with the 'endsub' is line #108 -- the line with the message that says: 
can't modify logical and (&&) in lvalue subroutine return.

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in it.

Not very helpful. Trying to run it under the debugger, I get a bit more information: 

> perl -d bin/dedup

Loading DB routines from perl5db.pl version 1.33
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

Can't modify logical and (&&) in lvalue subroutine return at /Users/la
+w.Bliss/bin/lib/Data/Vars.pm line 108, near "}"
BEGIN not safe after errors--compilation aborted at /Users/law.Bliss/b
+in/lib/Data/Vars.pm line 144.
 at /Users/law.Bliss/bin/lib/Data/Vars.pm line 144.
        require Data/Vars.pm called at bin/dedup line 21
        main::BEGIN() called at /Users/law.Bliss/bin/lib/Data/Vars.pm 
+line 144
        eval {...} called at /Users/law.Bliss/bin/lib/Data/Vars.pm lin
+e 144
Compilation failed in require at bin/dedup line 21.
 at bin/dedup line 21.
        main::BEGIN() called at bin/dedup line 21
        eval {...} called at bin/dedup line 21
BEGIN failed--compilation aborted at bin/dedup line 21.
 at bin/dedup line 21.
Debugged program terminated.  Use q to quit or R to restart,
  use o inhibit_exit to avoid stopping after program termination,
  h q, h R or h o to get additional info.
  DB<1>

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I.e. The problem might be closer to 144? What is there?... 
  BEGIN { #140
    if (require "Dbg.pm") {   # import if there, else not; no error if
+ not using TPe
      Dbg->import;
    } #143
  }  #144

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...Another closing brace and no '&&' in sight. That is called from line 21 in dedup: 
use Data::Vars \@fields, {mmap=>1, aio_respQ=>{}, examine_paths=>[], S
+YS_IO=>1,
              use_child_ra=>1};

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...This would seem to be a normal line to define & init vars in that module. Still no sign of logical 'AND'.

....Hmmm... I'm stumped. If anyone knows the secret code behind the above encrypted error message... and could explain what I should be looking for to fix, (or what I should fix), would appreciate it. I' be happy to post the rest of Data::Vars (~400 lines total), if people think that would be useful.

Anyone seen this type of error before...? The closest I can think of is when I have tried something like: 

$a==NULL && $a=xxx; (needs parens or 'and' instead of '&&').

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But don't see anything resembling that in the above or the rest of the code.

Ideas?

In reply to weird error message in middle-aged-perl(5.14) by perl-diddler

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