WHOA!! WHOA!!

I don't believe that your .pl script is working fine?
put these lines...

use strict;
use warnings;
[download]

at the beginning of your script!

use DBI;
my $driver = "mysql"; 
my $database = "marketplace_perl";
my $dsn = "DBI:$driver:database=$database";
my $userid = "root";
my $password = "root";
my $dbh = DBI->connect($dsn, $userid, $password )
   or die $DBI::errstr;###### 
my $dbh=connect_db(); ######### WHAT???#### !!!! #######
## my $dbh is defined twice!!!
my $sth = $dbh->prepare("SELECT UserEmail,UserPassword FROM pj_user wh
+ere UserEmail=? and UserPassword=?");
$sth->execute($UserEmail,$UserPassword);
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You redefine "my $dbh". That is a bad thing.

Your package is malformed.
See https://www.perlmonks.org/index.pl/Tutorials#Modules-How-to-Create-Install-and-Use
Show the code that calls the functions in the .pm module.
There aren't any executable statements in your .pm module and the subroutine names are not exported.