grep regex return substring but exclude comments

I want to get a substring from a file, but only from lines which are not preceded by an exclamation mark (which is the comment symbol in Fortran). I would prefer to use grep (but not bound to). For example: infile.txt: ``` calib_ss/baseline.txt !calib_ss/base_sharpe.txt ``` Desired result: ``` baseline ``` I got this far: ``` grep -Po "(?<=/)[^/.]*(?=\.)" infile.txt ``` which returns ``` baseline base_sharpe ``` To exclude the lines starting with ! I thought of combining the expression with ``` ^[^\!] ``` but I don't manage. Thanks in advance!