It removes the literal string %0D%0A. (More correct: it substitutes the forementioned string with nothing)

Please note that %0D is not CR until it is, and the same goes for %0A (LF). Some have replied this s/// removes CRLF sequences - that is NOT true! (It doesn't even remove all uri-encoded CRLF sequences: that would need /i)

2;0 juerd@ouranos:~$ perl -e'undef christmas'
Segmentation fault
2;139 juerd@ouranos:~$
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