Looks like you're connecting with ODBC. An ODBC connect string is a list of name-value pairs. For Windows authentication, omit UID=$usr;PWD=$pw; and instead say Trusted_Connection=Yes;.

For comparison, here's a code snippet I use to connect to SQL Server databases using DBI::ODBC. You may want to keep your value for DRIVER.

my $connect_string
    = 'DRIVER={SQL Server};'
    . "SERVER=$server;"
    . 'Trusted_Connection=Yes;'
    ;
my $dbh = DBI->connect(
    "dbi:ODBC:$connect_string",
    undef,
    undef,
    { RaiseError => 1 },
);
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