perl filename.pl remoteuser remoteserver
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The problem with your script is that you never use the command line args, and nothing is ever assigned to the variables "$remoteuser" and "$remoteserver". Do it like this (assuming that "remoteuser" is an alphanumeric string, and "remoteserver" is alphanumerics with periods):

#!/usr/bin/perl

die "Usage:  $0  remoteuser  remoteserver\n"
    unless ( @ARGV == 2 and $ARGV[0] =~ /^\w+$/ and $ARGV[1] =~ /^\w+(
+\.\w+)*$/ );

paranthesis( @ARGV );   # This is important

sub paranthesis {

    my ( $remoteuser, $remoteserver ) = @_;  # equally important

    system( 'scp', '/users/myuser/merc/rem_snew.pl',
        "$remoteuser\@$remoteserver:/users/$remoteuser/tmp/rem_snew2.p
+l" );

    my $result
        = `ssh $remoteuser\@$remoteserver perl /users/$remoteuser/tmp/
+rem_snew2.pl`;

    print "$result\n";
    system( 'ssh', "$remoteuser\@$remoteserver", 'rm',
        "/users/$remoteuser/tmp/rem_snew2.pl" );

}
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Also, you might want to try doing these other two commands first, before running the perl script:

ping -c 2 remoteserver
ssh remoteuser@remoteserver ls -d tmp
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