Cases not specified by the OP behave as follows:

"xxx{yyy zzz}" is split into "xxx{yyy" and "zzz}".
"{xxx yyy}zzz" is split into "{xxx yyy}" and "zzz".

@matches = /({[^}]+}|[^{\s]+)/g; might work better:

"xxx{yyy zzz}" is split into "xxx" and "{yyy zzz}".
"{xxx yyy}zzz" is split into "{xxx yyy}" and "zzz".