The term 'traverse', strongly suggests a recursive search of a hash of hash of ... of hash.

Traverse( \%yourhash, \$output, 'matchKey' );

sub Traverse{
    my $href = shift;
    my $oref = shift;
    my $match = shift;
    for my $key ( keys %$href ) {
        if ( ref( $href -> { $key }) eq 'HASH') {
            Traverse( $href -> { $key }, $oref );
        }
        else {
            ( $key eq $match ) and $$oref = $href -> { $key };
        }
    }
}
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