How do I modify the KEYS in a hash (copy)

NetWallah has asked for the wisdom of the Perl Monks concerning the following question: ⭐ (hashes)

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Re: How do I modify the KEYS in a hash (copy)⭐ by NetWallah (Canon) on Jul 21, 2004 at 21:45 UTC
To modify keys of a hash, it is necessary to copy it. The keys can be modified in the process of the copy by using 'map' like this: `my %Orig=('a b'=>44, 'c d'=>22, rr=>99); my %Copy = map {my $y=$Orig{$_}; #Save Copy of Val tr/ /_/; $_ => $y} keys %Orig; print qq(C: $_ => $Copy{$_}\n) for keys %Copy; print qq(O: $_ => $Orig{$_}\n) for keys %Orig;` [download] The trick here is to save a copy of the Value into "$y" before "$_" is modified. Once $_ is modified, the $Orig{$_} is no longer valid, so it must be saved into $y first.	[reply] [d/l]
Re: How do I modify the KEYS in a hash (copy)⭐ by jdporter (Paladin) on Feb 06, 2008 at 15:15 UTC
`my %Copy; @Copy{ map { tr/ /_/; $_ } keys %Orig } = values %Orig;` [download]	[reply] [d/l]
Re: How do I modify the KEYS in a hash (copy)⭐ by NetWallah (Canon) on Jul 29, 2004 at 17:09 UTC
Here is another way to modify KEYS in-place. This would be efficient in the case where there were a relatively small number of keys that required modification. Use the previous method (copy the hash) if the number of keys requiring modification is large. `my %o=(this=>33, 'th at'=>44, other=>55,'some thing'=>66,'or another'= +>77,none=>88); while (my ($k,$v)=each %o){ my $ModifiedK = $k; next unless $ModifiedK =~s/\s/_/; delete $o{$k}; #This is SAFE !! RTFM. $o{$ModifiedK}=$v; }; print qq(Mod: $_\t=>$o{$_} \n) for sort keys %o"` [download]	[reply] [d/l]
Re: How do I modify the KEYS in a hash (copy) by sen (Hermit) on Feb 06, 2008 at 11:56 UTC
Here is another way to modify the keys. `my %Orig=('a b'=>44, 'c d'=>22, rr=>99); my %Copy = map { $_ => $_=~ s/ /_/ } keys %Orig; print qq(C: $_ => $Copy{$_}\n) for keys %Copy;` [download] Originally posted as a Categorized Answer.	[reply] [d/l]
Re: How do I modify the KEYS in a hash (copy) by sen (Hermit) on Feb 06, 2008 at 14:42 UTC
Here is another way to modify the keys. `my %Orig=('a b'=>44, 'c d'=>22, rr=>99); my %Copy = map { $_ => $_=~ s/ /_/ } keys %Orig; print qq(C: $_ => $Copy{$_}\n) for keys %Copy;` [download] Originally posted as a Categorized Answer.	[reply] [d/l]
Re: How do I modify the KEYS in a hash (copy) by sen (Hermit) on Feb 06, 2008 at 14:42 UTC
Here is another way to modify the keys. `my %Orig=('a b'=>44, 'c d'=>22, rr=>99); my %Copy = map { $_ => $_=~ s/ /_/ } keys %Orig; print qq(C: $_ => $Copy{$_}\n) for keys %Copy;` [download] Originally posted as a Categorized Answer.	[reply] [d/l]