Quoting is in M$Win style:

C:\>perl -E "my $str='abc()[]xyz'; $str =~ s/[()\[\]]{1}/\"/g; say $st
+r;
abc""""xyz
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IOW, use a character class and escaping; both of which can be found in perldoc's perlre* pages. Note that the quantifier is redundant here, but could be useful were you trying to substitute two-at-a-time. OTOH, the /g modifier is NOT optional for this use case.

C:\>perl -E "my $str='a)bc([]xyz'; $str =~ s/[()\[\]]{2}/\"/g; say $st
+r;
a)bc"]xyz
[download]