Hello

my:
your subroutine needs temporary variables. You shouldn't use global variables, because another subroutine might also use the same variables.

local:
All subroutines called from the context of a local variable can access that variable.

$a='one';
$b='two';
sub1();

sub sub1 {
    local $a = 'three';
    my $b = 'four';
    sub2();
}

sub sub2 {
    print "\$a: $a\n";
    print "\$b: $b\n";
}
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Output

$a: three
$b: two
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