Converting PREV function to AmiBroker's equivalent

I have come across some AmiBroker code that uses the PREV function. However, it seems that the PREV function is not supported in AmiBroker, and I need to find an equivalent replacement for it.

L = 21;
St = Stdev(c, 5) / Ma(Stdev(c, 5), 10);
L = L * 0.75 / (St + 0.1);
L = If(L > Cum(x) - 13, Cum(x) - 13, L);
L := If(L < 1, 1, L);
VoEma = x * 2 / (L + 1) + PREV * (1 - 2 / (L + 1));
Plot(VoEma, "a", colorDefault);

help me to convert it to AmiBroker to achieve the same outcome.

Thank you

This has been answered already

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https://forum.amibroker.com/search?q=PREV%20MS