so...

my $foo = 3;
my $bar = "keyword mania";
my @blivitz = "(some set of value);
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within code blocks, subs, or suchlike, when you need them ...and only when you need them.

For example:

my $bar = "keyword mania";
... (do something);
... (and something more);
bax($bar);                    # send $bar to sub bax for further proce
+ssing
...(more code)

{                             # bare block
my @blivitz = ("7", '144', '1.16', "bat",);  # @blivitz values availab
+le only in this block
... do something with the elements of @blivitz;
}                             # end block

sub bax {                     # and here's the sub, bax
    my $foo = "3";
    ...do something to the value in $bar (a global) with $foo (availab
+le only in the sub);
    return (something);
}
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Make sure you understand scoping and the issues created by making your variables global.