$rc = system { "lskdfj" } "lskdfj"; unless( ok($rc == 255 << 8 or $rc == -1 or $rc == 256 or $rc == 512) ) { print "# \$rc == $rc\n"; } unless ( ok( $! == 2 or $! =~ /\bno\b.*\bfile/i or $! == 13 or $! =~ /permission denied/i or $! == 22 or $! =~ /invalid argument/i ) ) { printf "# \$! eq %d, '%s'\n", $!, $!; }