How do I push new data into an existing hash?

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

Originally posted as a Categorized Question.

Comment on How do I push new data into an existing hash?

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Re: How do I push new data into an existing hash? by merlyn (Sage) on May 22, 2000 at 19:00 UTC
`perldoc perldata`	[reply]
Re: How do I push new data into an existing hash?⭐ by KM (Priest) on May 22, 2000 at 19:01 UTC
Simple answer: $hash{key} = $val; Better answer: read perldata (perldoc perldata)	[reply]
Re: How do I push new data into an existing hash? by juo (Curate) on Apr 19, 2001 at 09:23 UTC
I want to add something to an existing key of a hash. $hash{key}=$val; will replace the content of key with a new content $val but will not add $val to the already existing content of key. If I try to use push to add the new value to the exisiting content then perl will give an error message : Type of arg 1 to push must be array (not hash elem.	[reply]
Re: Answer: How do I push new data into an existing hash? by arturo (Vicar) on Apr 19, 2001 at 15:23 UTC
Try `$hash{$key} .= $val;` if $hash{$key} is a (string) scalar, or `push @{$hash{$key}}, $val` if `$hash{$key}` is an array reference. See `perldoc perlref` and `perldoc perlreftut` for more on how to play with references.	[reply] [d/l] [select]
Re: How do I push new data into an existing hash? by BeernuT (Pilgrim) on Dec 29, 2001 at 20:50 UTC
use the '.=' operator `my $val = " World"; my %hash = (key => "Hello"); $hash{key} .= $val; print "$hash{key}";` [download] outputs 'Hello World' -bn	[reply] [d/l]
Re: How do I push new data into an existing hash?⭐ by Juerd (Abbot) on Dec 29, 2001 at 20:55 UTC
To append to one of the values, treat it like any other scalar and use the `.=` operator: `$hash{key} .= 'string'`. To merge two hashes into a third, use `%third = (%first, %second)`. To add a second hash to the first, use `@first{keys %second} = values %second` (You could use the merging technique, but that's very inefficient).	[reply]
Re: How do I push new data into an existing hash? by bradcathey (Prior) on May 18, 2005 at 08:44 UTC
And if it is a hash ref, use the arrow operator: `$hash -> {key} = $val;` [download]	[reply] [d/l]

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