$_ =~ s/<csp c="(\d+)">/"<colspec colnum=\"1\" colname=\"col1\"\/>" 
+x $1/egs;
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Note that qq// can be substituted for "" for the same effect. That way there will no need to escape a ". Similarly, / delimiter can be substituted with other character(s) which do(es) not appear in your pattern or replacement to avoid escaping of the delimiter character ...

$_ =~ s[<csp c="(\d+)">][qq(<colspec colnum="1" colname="col1"/>) x $1
+]egsx;
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