Pattern matching a string and getting matched values as string

Questions / Help
3

…but for the sake of the argument, this works:

iex(38)> "P" <> <<a::bytes-size(2)>> <> "W" <> b = "P11W3"
"P11W3"
iex(39)> a
"11"
iex(40)> b
"3"
iex(41)>

But of course it will only work for two-digit numbers.
Suggested further reading: Pattern-matching complex strings – The Pug Automatic

—EDIT—
Why didn’t the OP’s code work? Here are some hints. Hint 1:

iex(63)> "P" <> <<a::16>> <> "W" <> <<b::8>> = "P11W3"
"P11W3"
iex(64)> a
12593
iex(65)> b
51
iex(66)> <<a>>
"1"
iex(67)> <<a::16>>
"11"
iex(68)> b
51
iex(69)> a  
12593
iex(70)> <<b>>
"3"
iex(71)> <<b::8>>
"3"
iex(72)>

Hint 2:
12 593 (base 10) = 00110001 00110001 (binary) = 49 49 = “11” (ASCII)
51 (base 10) = 00110011 (binary) = 51 = “3” (ASCII)

See here: Bitstring and binary and here: Kernel.SpecialForms — Elixir v1.15.5

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