qw() quotes "words" so your expression is not being evaluated. See perlop : Quote and Quote-like Operators for more info.

Try:

my %g_tun = ( "R1", 100*32+1, "R2", 1, "R3", 100*32+1 );
[download]

or:

my %g_tun = (
    R1 => 100*32+1,
    R2 => 1,
    R3 => 100*32+1,
);
[download]

Hope this helps!