use enum qw[ CODE GRAPH START PATH SEEN ];
sub _pathsFrom2 {
    return $_[CODE]->( @{ $_[PATH] }, $_[START] )
        unless exists $_[GRAPH]->{ $_[START] };

    for ( @{ $_[GRAPH]->{ $_[START] } } ) {
        if( exists $_[SEEN]->{ $_[START] . "-$_" } ) {
            return $_[CODE]->( @{ $_[PATH] }, $_[START] );
        }
        else {
            _pathsFrom2(
                @_[ CODE, GRAPH ], $_,
                [ @{ $_[PATH] }, $_[START] ], 
                { %{ $_[SEEN] }, $_[START] . "-$_", undef }
            );
        }
    }
}


sub pathsFrom(&@) { _pathsFrom2( @_, [], {} ) }