Hi.

This is a patch to fix a specific case that makes 'M-x perldb' unable to
step through some code.

When debugging through a subroutine defined in an eval, perldb uses a slightly
different string to communicate the debugger position. This patch updates the
regex in gud-perldb-marker-filter to be able to parse this string.

An example of a "normal" string:
 ^Z^Z/tmp/tst.pl:6:0

An example of a sub-in-eval string that can now be parsed:
 ^Z^Z(eval 5)[/tmp/tst.pl:6]:3:0

Sample perl source that couldn't be stepped through before, and now can be:

 eval 'sub f
 {
   print 34;
 }
 ';

 f();