Or, try perldoc grep...

Perhaps something like:

  @Y = grep { $_ =~ /^magic/ } (<R>);
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That is the  grep EXPR LIST form of grep, which is exactly designed to search a list (here, the list of all records from filehandle <R>, split on the character or fixed length assigned to $/, q.v. in  perldoc perlvar) and return only the elements of the list (here, records in the file; probably lines, if you leave $/ at its default of "\n") that give "true" values for the EXPR.

Oh, and you really should run through perldoc or at least the Llama...