perl dbi postgresql uppercase problem

Hi folks,

I just begin to use the perl modules to query a Postgresql database and
faced the first problems (which are probably very trivial)

1.    first, is it possible to store the query in a file and invoke its
execution from perl (\i file.sql command from     Postgresql) ?

2.    second, I want to use PERL variables in an SQL query (for example
$var='R') but if I use them in the query, the Postgresql server return the
following error: Attribute 'r' not found ...  I did not ask for 'r'
attribute but for 'R'. Does any one know how to resolve this
uppercase/lowercase problem ?

Thanks in advance,
marco