get_nested_struct_val.pl

#!/usr/bin/perl
use 5.16.1;
use Data::Dumper;
use constant DFLT_STRUCT_KEY_SEP => '\.';

sub is_plain_scalar { defined($_[0]) &&  !ref($_[0]) && length($_[0]) }

my $get_struct_val_r;
$get_struct_val_rx = {
    'ARRAY' => sub {
#        print Dumper {'ARRAY'=>\@_};
        my $i = shift $_[1];
        length($i) && $i =~ /^-?\d+$/;
        $_[0] = $_[0][$i];
        $#{$_[1]} >= 0
            ? do {
                if (my $s = $get_struct_val_r->{ref $_[0]}) {
                    &$s
                } else {
                    undef
                }
              }
            : $_[0]
    },
    'HASH' => sub {
#        print Dumper {'HASH'=>\@_};
        $_[0] = $_[0]{shift $_[1]};
        $#{$_[1]} >= 0
            ? do {
                if (my $s = $get_struct_val_r->{ref $_[0]}) {
                    &$s
                } else {
                    undef
                }
              }
            : $_[0]
    }
};

sub get_struct_val {
    (my $refType = ref(my $struct = shift)) or return;
    my $pth = $_[0];
    is_plain_scalar($pth) or return;
    my $rxSep = is_plain_scalar($_[1]) ? $_[1] : DFLT_STRUCT_KEY_SEP;
    ($get_struct_val_r->{$refType} // sub { return })->($struct, [split qr($rxSep), $pth]);
}

my $hr = {
    'a' =>
    [
        {
            'b' =>
                {
                    'c' => [qw/d e f/]
                }
        }
    ]
};

print Dumper [ get_struct_val($hr, 'a.0.b.c.2') ];