The tabs are only used as a delimiter of the single 'cells' in the line, not in the text parts themself.
I tried both methods suggested here, the strip-method by Masem and yours, both work fine!
The advantage of the pattern-matching-method is that $1-$4 are free of \n's and \r's, which I had to cut out by substitution when using 'strip' afterwards, but it's just a question of personal favour. ;-)
Thanks to everyone here for the advice!

Bye, Micha