If I understand correctly, what you want to get is a result of FAIL if any of the test in the loop fails.

So, you can set to a true value (1) a variable before the loop and reset to false (0) whenever a single test fails. At the end of the loop the var has the value you expected.

my $result = 1;
foreach my $issued_CM_commands (@issued_commands){
  my $showconfig;
  $result = 0 if index("@showconfig", "$issued_CM_commands") == 0
}
print "\n--",$result ? 'PASS' : 'FAIL',"\n";
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(Untested)