Binary String pattern matching

Hello all

I am learning Erlang and have stuck to the following problem.
How to write a function with pattern matching when the parameter is a
binary string.

I have a list of binary strings e.g.
<<3123CHF>>
<<341424343EUR>>
<<14143US>>

I am trying to create a function that matches according to a pattern.

currrency_to_credits({cur, <<A, "CHF">>}, Acc)
  when Value >= <<"1000">>, Value =< <<"10000">> ->
     {chf, Acc + A};
currrency_to_credits({cur, <<A, "EUR">>}, Acc)
  when Value >= <<"1000">>, Value =< <<"10000">> ->
     {eur, Acc + A};
currrency_to_credits({cur, <<A, "US">>}, Acc)
  when Value >= <<"1000">>, Value =< <<"10000">> ->
     {us, Acc + A};

But this does not seem to be the right way.
How can I create a pattern for binary string?
will it work better for list string? How?

Thank you
Nikolas