Your error appears to be here my firend.

-e 's/[0-9][0-9][TFX][TFX][TFX][TFX]/&\
/g \

Simply swap it for this and I believe it will work...

-e 's/[0-9][0-9][TFX][TFX][TFX][TFX]/\
&/g \

Pretty simple really...
But in future I suggest you dont post your university assignments on notice boards. Their assigned to you and only you!

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