in reply to What does this mean?

That last bit is a subroutine prototype in Perl. See perlsub for more information. It's generally not used very widely nor accepted as a best practice, but it can give you some clues on what the subroutine might be expecting.

In this case, I believe ($;$) is the prototype for 2 scalar values.

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Re^2: What does this mean?
by AnomalousMonk (Archbishop) on Jul 08, 2014 at 15:14 UTC

    In addition, as  convertCitifile2Dataset() is invoked as a class method, its prototype is completely ignored. 

    c:\@Work\Perl>perl -wMstrict -le
"package Foo;
 sub foo ($;$) { print qq{(@_)}; }
 ;;
 package main;
 Foo->foo;
 Foo->foo();
 Foo->foo(1, 2, 3, 4, 5, 6);
"
(Foo)
(Foo)
(Foo 1 2 3 4 5 6)

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