for ( $x .. $y ) {          # some loop

# ... skipped ...

# fragment #1:

    next unless exists $gs_val-> { HT };

    my $ht = $doc-> getValue( $gs_val-> { HT });
    next unless exists $ht-> { Default };

    my $df = $doc-> getValue( $ht-> { Default });
    next unless exists $df-> { TransferFunction };

    my $tf = $doc-> getValue( $df-> { TransferFunction });
    next unless $tf eq 'Default;
    
# ... skipped ...

# fragment #2:

    next unless $doc-> getValue( 
                $doc-> getValue( 
                $doc-> getValue( 
        $gs_val-> { HT }               || next )
               -> { Default }          || next )
               -> { TransferFunction } || next ) eq 'Default';

# ... skipped ...
}