Here is my try,

my $aref = [{DB => 'Alpha',
             SOURCE => 'here'},
            {DB => 'Beta',
             SOURCE => 'there'},
            {DB => 'Gamma',
             SOURCE => 'someplace'}];
foreach $arr (@$aref) {
    push @list,$arr->{DB};
}
print $_."\n" for @list;
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