If you want to trundle through an arbitrarily deep reference tree with grep-like syntax, it's actually fairly easy to implement:

    use 5.016; # For __SUB__, or pre-declare $grep and use $grep->() s
+yntax

    sub ref_grep(&$) {
        my ($wanted, $ref) = @_;
        my $seen = {}; # Refs we've already seen (avoid circular refs)
        my @found;     # Result list
        
        my $grep = sub {
            my ($ref, $path) = @_;
            return if ref $ref and $seen->{$ref}++;
            { $_ = $ref; push @found, $path if $wanted->() }
            for (ref $ref) {
                when ('HASH') {
                    __SUB__->($ref->{$_}, $path."->{$_}") for sort key
+s $ref;
                }
                when ('ARRAY') {
                    __SUB__->($ref->[$_], $path."->[$_]") for sort key
+s $ref;
                }
            }
        };
        $grep->($ref, '');
        return @found;
    }

[download]

Invocation is just like grep:

    say "Found value2: \$hash$_" for ref_grep { $_ eq 'value2' } $hash;

It's not limited to scalars, either; the BLOCK can perform any test it likes.

Of course, this is not without limitations. Support for nested objects, tests based on the path itself, pruning, etc., would take more work, and I'd certainly not try much harder to re-invent this wheel. What I'm saying is, take this as a starting point.

use strict; use warnings; omitted for brevity.

In reply to Re: grepping the location of a value from a datastructure by rjt
in thread grepping the location of a value from a datastructure by rastoboy

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