map works... but there is a feeling that it is not needed. If I do it, I will simply:

use strict;
use warnings;
use Data::Dumper;

my $AoH_orig = [ { 'title' => 'aaa-aaa',
                   'name'  => 'tom' },
                 { 'title' => 'bbb-bbb',
                   'name'  => 'kathy' },
                 { 'title' => 'ccc-ccc',
                   'name'  => 'bill' } 
                 ];

for (@$AoH_orig) {$_->{'title'} =~ s/-/_/g};

print Dumper($AoH_orig);
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Which gives you what you wanted:

$VAR1 = [
          {
            'name' => 'tom',
            'title' => 'aaa_aaa'
          },
          {
            'name' => 'kathy',
            'title' => 'bbb_bbb'
          },
          {
            'name' => 'bill',
            'title' => 'ccc_ccc'
          }
        ];
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#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;

my $AoH_orig = [ { 'title' => 'aaa-aaa',
                   'name'  => 'tom' },
                 { 'title' => 'bbb-bbb',
                   'name'  => 'kathy' },
                 { 'title' => 'ccc-ccc',
                   'name'  => 'bill' }
                 ];

#try mapping
print Dumper ($AoH_orig);

my $AoH_new = map { $_->{'title'} =~ s/-/_/g } @$AoH_orig;

print Dumper($AoH_orig);
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$VAR1 = [
          {
            'name' => 'tom',
            'title' => 'aaa-aaa'
          },
          {
            'name' => 'kathy',
            'title' => 'bbb-bbb'
          },
          {
            'name' => 'bill',
            'title' => 'ccc-ccc'
          }
        ];
$VAR1 = [
          {
            'name' => 'tom',
            'title' => 'aaa_aaa'
          },
          {
            'name' => 'kathy',
            'title' => 'bbb_bbb'
          },
          {
            'name' => 'bill',
            'title' => 'ccc_ccc'
          }
        ];
[download]

All dashes (-) are replaced with underscore (_) isn't that what you are trying?

I probably will not use map for this as you are not returning a list back. I would stick with your for for idea.

 $_->{'title'} =~ s/-/_/g for(@$AoH_orig); should work just fine (i think)

cheers

SK

for (@$AoH_orig) { $_->{title} =~ s/-/_/g; }
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my $AoH_new = [ map { my %tmp = %$_; $tmp{title} =~ s/-/_/g; \%tmp } @
+$AoH_orig ];
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• my $AoH_new = map ...
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  map generally returns a list, not an array ref. Here, you're calling it in scalar context, so it actually returns the number of items in its return list. This isn't what you want, judging by your variable names.

• my $AoH_new = map { $AoH_orig->[$_]{'title'} =~ s/ /_/g } @$AoH_orig;
  [download]

  For each item in the list, map executes the block with that item aliased to $_. But here you are treating $_ as an array index for @$AoH_orig, not as an element of $AoH_orig. Either map over the actual indices (0 .. $#$AoH_orig), or use something closer to your second example, which is:

• my $AoH_new = map { $_->{'title'} =~ s/ /_/g } @$AoH_orig;
  [download]

  Each time map executes the block, it accumulates the return value of the block in a list, and finally returns the list. In this case, you're accumulating the return values of "$str =~ s///g" statements. But these statements only return the number of changes made to the string. Again, it seems like you want modified copies of the strings in $AoH_orig, with a similar structure -- not a list of the number of changes made to each string.
• Since $_ is aliased to the elements of @$AoH_orig, the s/// inside the map actually modifies things inside of $AoH_orig. Again, probably not what you want.
• Even fixing all that, if you want to replicate the structure of $AoH_orig, you need to have a level of hashes in there somewhere. If you want an AoH, then each item in the array needs to be a hashref -- the map statement must return a list of hashrefs. So the map's block must evaluate to a hashref each time.

my @AoH_new = map {       ## store the result in an array
    my %h = %$_;          ## make a copy of each hashref
    $h{title} =~ s/ /_/g; ## modify a value in the hash copy
    \%h;                  ## return a ref to that copy
} @$AoH_orig;
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use Storable 'dclone';
my $AoH_new = dclone $AoH_old; ## copy the old structure

## change an item in each hash in the new copy
$_->{title} =~ s/ /_/g for @$AoH_new;
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Update: changed "$h->" to "$h" in my example. Thanks Errto.

my @AoH_new = map { $_->{'title'} =~ s/-/_/g; $_  } @$AoH_orig;
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my $Aref_new =[ map {(my $x=$_->{'title'}) 
                 =~ s/ /_/g;$x } @$AoH_orig]; 
print Dumper(\$Aref_new);
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When I did this, I got lots of warnings, such as

Use of reference "HASH(0x224f58)" as array index at scratch.pl line 23
+.
Use of uninitialized value in substitution (s///) at scratch.pl line 2
+3.
Use of reference "HASH(0x18916bc)" as array index at scratch.pl line 2
+3.
Use of uninitialized value in substitution (s///) at scratch.pl line 2
+3.
Terminating on signal SIGINT(2)
Use of uninitialized value in substitution (s///) at scratch.pl line 2
+3.
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can you point me to a good tutorial?

Perfect, thanks (for anyone interested, this is a great tutorial).


—Brad
"The important work of moving the world forward does not wait to be done by perfect men." George Eliot