-F does allow multicharacter separators (at least true for me on bash shell and gawk) $ echo 'Sample123string42with777numbers' | awk -F'[0-9]+' '{print $2}

-F does allow multicharacter separators (at least true for me on bash shell and gawk) $ echo 'Sample123string42with777numbers' | awk -F'[0-9]+' '{print $2}' string