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Actually it looks like if the hash itself is not shared, any changes to keys will not affect other running threads. This includes deleting keys (the key/value will still be there in other threads). Only changes to the shared values will affect other running threads (including undefining them).

use strict; use threads; use threads::shared; my %hash = ( 'a' => 'foo', 'b' => 'foo', 'c' => 'foo', 'd' => 'foo' ); share($hash{$_}) foreach('a'..'f'); my $tid = 0; foreach my $key('a'..'f') { if(exists $hash{$key}) { if(defined $hash{$key}) { print "$key => $hash{$key} in thread $tid\n"; } else { print "$key => undef in thread $tid\n"; } } else { print "$key does not exist in thread $tid\n"; } } my $th1 = async { $tid = 1; print "thread $tid started\n"; sleep 2; foreach my $key('a'..'f') { if(exists $hash{$key}) { if(defined $hash{$key}) { print "$key => $hash{$key} in thread $tid\n"; } else { print "$key => undef in thread $tid\n"; } } else { print "$key does not exist in thread $tid\n"; } } print "delete b from thread $tid\n"; delete $hash{'b'}; print "undefine d from thread $tid\n"; undef $hash{'d'}; print "setting f => foo in thread $tid\n"; $hash{'f'} = 'foo'; }; my $th2 = async { $tid = 2; print "thread $tid started\n"; sleep 3; foreach my $key('a'..'f') { if(exists $hash{$key}) { if(defined $hash{$key}) { print "$key => $hash{$key} in thread $tid\n"; } else { print "$key => undef in thread $tid\n"; } } else { print "$key does not exist in thread $tid\n"; } } }; sleep 1; print "delete a from thread $tid\n"; delete $hash{'a'}; print "undefine c from thread $tid\n"; undef $hash{'c'}; print "setting e => foo in thread $tid\n"; $hash{'e'} = 'foo'; $th1->join(); $th2->join(); foreach my $key('a'..'f') { if(exists $hash{$key}) { if(defined $hash{$key}) { print "$key => $hash{$key} in thread $tid\n"; } else { print "$key => undef in thread $tid\n"; } } else { print "$key does not exist in thread $tid\n"; } }
a => foo in thread 0 b => foo in thread 0 c => foo in thread 0 d => foo in thread 0 e => undef in thread 0 f => undef in thread 0 thread 1 started thread 2 started delete a from thread 0 undefine c from thread 0 setting e => foo in thread 0 a => foo in thread 1 b => foo in thread 1 c => undef in thread 1 d => foo in thread 1 e => foo in thread 1 f => undef in thread 1 delete b from thread 1 undefine d from thread 1 setting f => foo in thread 1 a => foo in thread 2 b => foo in thread 2 c => undef in thread 2 d => undef in thread 2 e => foo in thread 2 f => foo in thread 2 a does not exist in thread 0 b => foo in thread 0 c => undef in thread 0 d => undef in thread 0 e => foo in thread 0 f => foo in thread 0

In reply to Re^4: PerlIO file handle dup by chris212
in thread PerlIO file handle dup by chris212

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