G'day georgecarlin,

The select(undef, undef, undef, $float_seconds); construct was a Perl4 (and earlier) solution for sleeping for fractional seconds.

The usleep() function of Time::HiRes has been available since 1996 (earliest CPAN reference I could find: Time::HiRes v1.02) and has been part of the Perl distribution since Perl v5.8.0 (perl58delta - what is new for perl v5.8.0). It should be available for your immediate use without requiring any installation or other activity on your part. If you're using an earlier version of Perl (perl -v on the command line will tell you), I'd recommend upgrading: v5.18.1 is the current version.

Add this line near the top of your code:

use Time::HiRes qw{usleep};
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The usleep() function takes an argument in microseconds, so replace instances of

select(undef, undef, undef, 0.25);
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with

usleep 250000;
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You can do this in your current code, the ++solution provided by smis (above) or in whatever other solution you might choose.

[Update: Oops! I wrote "microseconds" and then provided a number in milliseconds: s/250/250000/]

Thank you for pointing this out to me. Version is 5.8.4, so I have replaced all corresponding occurences in the script.

A perfect use-case for closures!

You can use a loop to dynamically generate the callback subs passed to expect():

my @actions = (
  [qr/pattern1/, "response1", sub { dostuff.. }       ],
  [qr/pattern2/, "response2", sub { do_other_stuff.. }],
  [qr/pattern3/, "response3", sub { do_this_stuff.. } ],
);

$exp->expect($timeout, map {
  my ($pattern, $response, $code) = @$_;
  [ $pattern, sub {
      select(undef, undef, undef, 0.25);
      $exp->send($response);
      $code->();
    }
  ];
} @actions);
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In Perl, every subroutine which uses lexical variables that were declared outside of it, will use the version of those variables from the time the sub was created. The technical way of saying it, is that the subroutine becomes a "closure" - for an in-depth explanation see e.g. Closure on Closures.

So in this case, each copy of the "sub {...}" callback created inside the "map {...}" loop, will remember the corresponding values of $response and $code.

Update: If you want, you can replace  $code->();  with  goto &$code;  to avoid the nested function call, and thus gain a tiny performance increase. The down-side is that you must remember not to add any additional commands to the closure after that line, because the goto will never return. (See the bottom two paragraphs of goto for an explanation.)

This is not only exactly what I was looking for, it is very well explained for a beginner like me and with further documentation linked. Thank you very much for taking the time and esp. for such a great response!

Can you provide a tangible example? This is really hard to follow.