use strict;
sub build_lazy {
    my ($name, $callback, @params) = @_;
    
    my $var;
    no strict 'refs';
    *$name = sub {
        $var = $callback->(@params) unless defined $var;
        $var;
    };
}

build_lazy( 'dbh', sub { print @_ }, 'hi');
print dbh(), dbh(); # hi11