If a hash has only a single value, is there a nice way to get the value without knowing the key and without a foreach loop? The following code illustrates what I've got (with some extra layers, in case any kind monk cares to critique it and help me improve). I need to get the sourcefile for the WinBinary component; it seems a bit weird to use foreach because the "target" key only ever has a single value but can vary between data files. I need to avoid storing the value of the "target" key. 
 
#--------------------- component -- targetver -- Arr -- datahash
#
#   $ComponentData = {
#                     'key_A' =>  {
#                                   '6.0' => [
#                                                  {
#                                                    'FILENAME' => 'fi
+lename',
#                                                    'VERSION'  => 've
+rsion';
#                                                     ooo
#                                                  },
#                                                  ooo
#                                             ],
#                                    ooo
#                                  },
#                       ooo
#                      }
#
# where ooo represents potential repetition
#

my %ComponentData; 

sub store_data {
    my $parmref = shift;  # input parameter is a hash ref
    my $component   = $parmref->{COMPONENT}; 
    my $tgtver      = $parmref->{TGTVER};    
    my $version     = $parmref->{VERSION};
    my $file        = $parmref->{FILENAME};   
    
    # store data
    $ComponentData{$component}->{$tgtver} = [] unless exists $Componen
+tData{$component}->{$tgtver};
    my $href = {};
    $href->{VERSION} = $version;
    if( $file ){ 
        $href->{FILENAME} = $file 
    };
    push @{$ComponentData{$component}->{$tgtver}}, $href;
}



sub oldstore_data {
    # store a data hash
    $ComponentData{$component}->{$targetver} = [] unless exists $Compo
+nentData{$component}->{$targetver};
    my $href = {};
    if( $file     ){ $href->{FILENAME} = $file };
    if( $checksum ){ $href->{CHECKSUM} = $checksum };  # etc
    push @{$ComponentData{$component}->{$targetver}}, $href;
    return;
}

# show all the data
sub show_all_data {
    foreach my $comp ( sort keys %ComponentData ) {
        print "- - - - -\n";
        print "component:$comp\n";
        foreach my $tgtver ( sort keys %{ $ComponentData{$comp}} ) {
            print "  target:$tgtver\n";
            for my $href (@{ $ComponentData{$comp}{$tgtver} }) {
                print "    version:", $href->{VERSION},"\n";
                if( $href->{FILENAME} ) {
                    print "    file: ", $href->{FILENAME},"\n";
                }else{
                    print "    file: undefined\n ";
                }
            }
            print "\n";
        }
    }
}

while (<DATA>) {
    chomp;
    $_ =~ s/ +//g;
    my ($comp, $tgtver, $version, $file ) = split /\|/;
    #print "comp=$comp, tgtver=$tgtver, version=$version, file=$file;\
+n";
    my $href = {};
    $href->{COMPONENT} = $comp;
    $href->{TGTVER}  = $tgtver;
    $href->{VERSION} = $version;
    if( $file ){
        $href->{FILENAME}  = $file;
    }
    store_data( $href );
}

show_all_data ;

# is there a nice way to get the value I want here, without foreach?
foreach my $xstgt ( sort keys %{ $ComponentData{ "WinBinary" }} ) {
    my $specialsource = ${@{ $ComponentData{ "WinBinary" }{$xstgt}}[0]
+}{FILENAME};
    print "what I want is $specialsource\n"
}

print "done/n";


# component       target   version    sourcefile
__DATA__
WinBinary         | 4.0 | 7.8.9.123 | winbinsrc
NetBinary         | 5.0 | 10.1.2.34 | netbinsrc
SupplementalPack  | 6.0 | 1.6.0
SupplementalPack  | 6.1 | 1.6.0
Hotfix            | 6.0 | NULL | hotsource01
Hotfix            | 6.0 | NULL | hotsource02
Hotfix            | 6.1 | NULL | hotsource03
Hotfix            | 6.1 | NULL | hotsource04

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In reply to Can I avoid loops getting the single value from a hash without knowing the key? by anadem

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