How do I concatenate 2 strings in NSIS

Question

How do I concatenate 2 strings in NSIS?

Answer 1

StrCpy $1 "one string"

StrCpy $2 " second string"

MessageBox MB_OK "$1$2"

Answer 2

StrCpy $1 "Hello"

StrCpy $2 "World"

StrCpy $3 "$1 $2"

DetailPrint $3