Hi I am new to Perl

i have initial variable like

my $ini=4;
my $last=2;
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i am creating hash in the following way

my %result=(

SAS1=>$ini-$last,
SAS2=>$last-$ini,
SAS3=>$ini-$last
);
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then i am printing the hash values

O/P will be like this

2

-2

2

OK

now i wants to change the value of variable like

my $ini=10;
my $last=5;
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Now my problem is whenever i change the those variable

then those values should reflect in the hash %result

and whenever i print the hash it should display the latest result like

5

-5

5

can anybody help me :-)