Hi,
if you are interested in learning Verilog only, I recommend to use a
free development platform. Therefore Modelsim shouldn't be your first
choice.
If you plan to go further than simply learning Verilog, e.g. develop
FPGA designs, it depends on which device you choose for your projects.
Here is a small list with free software alternatives:
Manufacturer - Software Kit
------------------------------
Intel/Altera - Quartus
Xilinx - ISE/Vivado
Lattice - Diamond (Simulator included only in Windows version!)
Microsemi - Libero
For Xilinx and Lattice I know there is free Verilog support.