To install p5.28-math-mpfi, run the following command in macOS terminal (Applications->Utilities->Terminal)
sudo port install p5.28-math-mpfi
To see what files were installed by p5.28-math-mpfi, run:
port contents p5.28-math-mpfi
To later upgrade p5.28-math-mpfi, run:
sudo port selfupdate && sudo port upgrade p5.28-math-mpfi
Reporting an issue on MacPorts Trac
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Though anyone may search Trac for tickets, you must have a GitHub account in order to login to Trac to create tickets.