A JS vector that shows what characters are allowed in-between operators.
"1337"$[chr]in$[chr]log($[i])"1337"⟦09⟧in0x09alert(9)"1337"
in
alert(10)"1337"0x0Bin0x0Balert(11)"1337"0x0Cin0x0Calert(12)"1337"0x0Din0x0Dalert(13)"1337" in alert(32)"1337" in alert(160)"1337" in alert(5760)"1337" in alert(8192)"1337" in alert(8193)"1337" in alert(8194)"1337" in alert(8195)"1337" in alert(8196)"1337" in alert(8197)"1337" in alert(8198)"1337" in alert(8199)"1337" in alert(8200)"1337" in alert(8201)"1337" in alert(8202)"1337"
in
alert(8232)