Self-excited thermoacoustic instability is undesirable in propulsion and power generation systems due to its detrimental effects. In this work, we conducted experimental demonstration study of applying bias-flow perforated liners on attenuating self-excited thermoacoustic oscillations in a premixed T-shaped combustor. For this, two perforated liners with different porosities and variable bias flow rate are experimentally tested and compared. It is found that in the absence of bias flow (cooling flow), the premixed flame can produce and sustain limit cycle oscillations. The amplitude and frequency of the dominant thermoacoustic mode are approximately 215 Hz and 140 dB. However, as the cooling flow velocity is increased to 5.5 m/s, the limit cycle oscillations are completely attenuated. More than 50 dB sound pressure level reduction is achieved. High-frequency modes are dampen by more than 25 dB. Further experimental test is conducted on the perforated liner with a porosity of 2.9%. Similar attenuation effect is achieved. Finally, during the transient growth process, dominant mode switching from high (non-harmonic) to low frequency is observed. The present work shed lights on the optimum design of perforated liner on attenuating thermoacoustic instability and the dynamic behaviours of the transient growth process.