Although seemingly undocumented, getopts() stops parsing as soon as it hits a non-switch formatted argument (an argument that doesn't have a leading dash) in the command line that doesn't have a preceeding switch that accepts a parameter.

Assuming you have getopts (":abcd:e:"), the following cases apply:

getopts() returns a non-zero value, the hash contains -a=1, -d=5, and @ARGV is 0 length.

getopts() returns a zero value, the hash contains -a=1, -d=5, and @ARGV is 0 length.. A warning is also printed from inside getopts()

returns a zero value, the hash contains -a=1, and @ARGV contains 'xxx', '-d', '5'

You can use the fact that @ARGV still contains values to print an error message. Or, you could get more sophisticated, and do something with the unparsed argument. Since the arguments are dropped from @ARGV as they are parsed, you could stay in a loop until @ARGV is 0, print "I don't recognize this argument: $@ARGV[0]\n", shift @ARGV, and call getopts() again. This will result in your hash containing all the valid arguments that were on the command line, and personalized messages for ones that are invalid.

--Chris