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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def generate(env):
 """ Add Builders and construction variables for the Visual Age FORTRAN compiler to an Environment. """

    path, _f77, _shf77, version = get_xlf77(env)
    if path:
        _f77 = os.path.join(path, _f77)
        _shf77 = os.path.join(path, _shf77)

    f77.generate(env)

    env['F77'] = _f77
    env['SHF77'] = _shf77