Hi!

I never used our, so all this looks a bit strange for me :-). Anyway, try the following:
Change this

 
our(@ratio, @ratiobox, @concentration, @wtPercent, @density, %chemname
+);
my (@concentrationbox, @densitybox, @wtpercentbox);
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to this:

our(@ratio, @ratiobox, @concentration, @wtPercent, @density, %chemname
+, @wtpercentbox);
my (@concentrationbox, @densitybox);
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And this:

map{$_->configure(-textvariable=>\$wtPercent[2])}@wtpercentbox;
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to this:

map{$_->delete(0,'end')}@wtpercentbox;
for my $i (0..$#wtpercentbox) {
        $wtpercentbox[$i]->insert('end',$wtPercent[$i]);
}
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It should work now (I hope so :-))

mawe