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Subroutine Prototypes Prototype Definitions

Perl uses its variable dereferencing symbols as prototype parameter definition tags

Symbol	Declares
$	A scalar argument
@	A list argument
&	A subroutine argument
\$	A scalar reference argument
\@	A list reference argument
\%	A hash reference argument

Specifying multiple tags declares additional arguments

sub MySubroutine2($$\@$) { EXPR }
# Takes two scalars, a list reference, and a third scalar