The text $main in your eval is being taken as a variable of that name. Escape the $.
But you shouldn't need to use eval. This works for me:
my $var = 'fred';
${"main::$var"} = 12345; ## set main::fred = 12345
With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
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In the absence of evidence, opinion is indistinguishable from prejudice.