As others have pointed out, perlre or perlretut are recommended reading, because this is a very important and basic construct in regular expressions.

In a regex, [] surround a "character class", meaning that it matches any of the characters inside the square brackets.

Since split divides a string based on its delimiter regex, in this case, your input string is being split on any of the { } , * characters.

$ $ perl -e'print "$_\n" foreach split /[,{}*]/,"this{is*a}test,of"'
this
is
a
test
of
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