Good to see that you're using strict. If you change line 2 to

my %hash = ($values[0] => [$values[1]]);
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then the warning will go away. However, you still have a problem because %hash is local to the while() loop. When you get to the foreach loop it will have gone out of scope and you won't get any output. Try this instead:

my %hash;
while ($values = fetchrow_array()){
push (@{$hash{$values[0]}}, values[1]);
push (@{$hash{$values[0]}}, values[2]);
}
foreach $value (keys %hash){
print "\$hash: @{$hash{$value}}\n";
}
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You may wonder how it's possible to use an undefined value as an array reference. This is a bit of Perl magic called autovivification.