use warnings;
use strict;
use YAPE::Regex::Explain;
my $re = '[\w().-]*\(?([\w.-])?\)?\s*->\s$';
print YAPE::Regex::Explain->new($re)->explain();

__END__
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Do you really need those capturing parentheses? All the examples in the doc show pretty simple regexes for prompt. Maybe you could try simplifying the regex until it passes some simple case.

is throwing an error

Ah, thank you! I had forgoten all about YAPE::Regex::Explain.

The capturing parentheses are needed to pass the expression to a different function.

What is the error message?

I'm not entirely sure yet why it's throwing an error. It's an internal error check with Net::Telnet. After much debuging I've determined errmode->mode is being set to die after passing this regex to the prompt method. This causes another function, error(), to exit the script with die, but it doesn't print the error message. I was hoping maybe there was something I was missing with the regex causing the behavior

Should the last part be ->\s*$/' perhaps (note the \s*)>

You might use //x to make your regex a bit more readable. Like this:

'/ [\w().-]* \(? ([\w.-])? \)? \s* -> \s* $ /x'
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You could even use more than one line and comments to make the regex much clearer, but since we need to store it in a string I left that out

I don't see anything which would produce an error but the regex part between the two parens (and the parens themselves) will never match anything because the first part already matched it.