Canadian postcodes take the form A1A 1A1, with an alphabetic character preceding a numeric

digit, which in turn is followed by an alphabetic character. That in turn is followed by an optional

space character, which is followed by one numeric digit, followed by one alphabetic character,

followed by a numeric digit.

Considering the sample file below, write a regular expression to only match valid Canadian

postcodes (highlighted in grey)

T3Z 3N7

D8R 8C4

RR4 88D

P9C 3Q4

V2X 3RU

V5R8S4

M8N 7LK

J1M6U4

S1B 2R9

88B U2L

D7R 7L2

F9Z6G4