A list in Perl is pretty much like an array although there are some fine differences between these two concepts. I think your nomenclature {} vs () and description may not be the best. The {} does not describe an array or a "list".

An "exit code" says to me that this is single integer value from returned to the O/S, not a multi-valued thing or data structure - an "exit code" is an integer in Windows or Unix.

I think you mean to check the return array value from a subroutine? This code checks that the main program only got one returned value and that that single value is "3".

#!usr/bin/perl -w
use strict;

my @result;

@result = X();
print "array returned from sub X is: ", @result,"\n";
if ((@result == 1) and ( grep {$_ == 3}@result ))
{
   print "Sub X passes the test", @result,"\n";
}
else
{
   print "@result: for Sub X fails the test\n";
}

print "\n";


@result = Y();
print "array returned from Sub Y is: ", @result,"\n";
if ((@result == 1) and ( grep {$_ == 3}@result))
{
   print "Sub Y @result passes the test\n";
}
else
{
   print "Sub Y @result fails the test\n";
}

print "\n";


sub X
{ 
   return (1,2,3,4,5,6,7,8,9);
}

sub Y
{
   return (3);
}

__END__
array returned from sub X is: 123456789
1 2 3 4 5 6 7 8 9: for Sub X fails the test

array returned from Sub Y is: 3
Sub Y 3 passes the test
[download]

Update: well if the OP's intention is that should work for anything but 3, then the modifications should be obvious.