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in reply to Re: How Do I End Up With a Larger Number of Hash Keys Here?
in thread RESOLVED - Autovivification: How Did I End Up With a Larger Number of Hash Keys Here?

Uh .. no. 

tab@music4:~ $ perl -de 1

Loading DB routines from perl5db.pl version 1.51
Editor support available.

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

main::(-e:1):   1
  DB<1> %hash = ();

  DB<2> use Data::Dumper;

  DB<3> print Dumper(\%hash)
$VAR1 = {};

  DB<4> if ( exists $hash{nothing} ) { print "Wow.\n"; }

  DB<5> !3
print Dumper(\%hash)
$VAR1 = {};

  DB<6>

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For me, the whole point of using exists is to avoid doing autovivification.

But the example used a two level hash .. so I answered the wrong question. Ugh.

Alex / talexb / Toronto

Thanks PJ. We owe you so much. Groklaw -- RIP -- 2003 to 2013.

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Re^3: How Do I End Up With a Larger Number of Hash Keys Here?
by pryrt (Abbot) on Mar 03, 2020 at 19:40 UTC
    Uh .. no.

    Actually, yes. 1nickt had a HoH, not just a simple hash. Intervening levels can and do get created, even when called by exists

    > perl -de 1

Loading DB routines from perl5db.pl version 1.27
Editor support available.

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

main::(-e:1):   1
  DB<1> %hoh = ();

  DB<2> use Data::Dumper;

  DB<3> print Dumper(\%hoh)
$VAR1 = {};

  DB<4> if (exists($hoh{nothing}{second})) { print "wow.\n"; }

  DB<5> !3
print Dumper(\%hoh)
$VAR1 = {
          'nothing' => {}
        };

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