Table-name as parameter to plpgsql

The following function failes to compile:

CREATE OR REPLACE FUNCTION test_func(p_table_name VARCHAR) RETURNS VOID AS $$
BEGIN
INSERT INTO p_table_name(some_field) VALUES('some_value');
END;
$$ LANGUAGE plpgsql;

Gives:
ERROR: syntax error at or near "$1"
LINE 1: INSERT INTO $1 (some_field) VALUES('some_value')

Any hints on how to use function-parameters as table-names like I'm trying to
above?

--
Andreas Joseph Krogh <andreak(at)officenet(dot)no>
Senior Software Developer / Manager
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