The humble "plus" operator is actually quite sophisticated.

Expression	Result
1  +  1	2
-3  +  27.2	24.2
"1"  +  "1"	"11"
"cat"  +  1	"cat1"
1  +  "cat"	"1cat"
"cat"  +  "ch"	"catch"
"cat"  +  "   door"	"cat door"
"27.15"  +  "0.2"	"27.150.2"

These examples show the plus operator doing three quite different things:

• If both items are numeric, it does an arithmetic addition
• If both items are strings, it does a string join
• If the items are mixed, it does what it can