package Your::SQL::Utils;

use DBI;
use DBD::Pg;

sub new {
    my ($class, ...) = @_;
    bless { dbh =>  _connect() } => $class;
}

sub _connect {
    ...
    return $dbh;
}

sub dbh { 
    my ($self) = @_;
    $self->{dbh};
}

sub some_query {
    my ($self, ...) = @_;

    ...
    my $sth = $self->dbh->prepare(...);
    ...
    $sth->execute(...);
    ...
}

sub other_query { ... }

##</code><code>##

# your_prog.pl

use Your::SQL::Utils;
use Getopt::Long;

my $query;
GetOptions('query=s' => \$query) or die "...";

my $util = Your::SQL::Utils::->new();
$util->$query();

##</code><code>##

$ your_prog.pl -q some_query