use strict;

####################
# in summary:
#  - regex 3 (same as originally posted more or less) 
#             gives the 'wrong' results
#  - regex 2 (eq regex 2 but wothout the \s* part before the letter match) 
#             gives the 'right' results
#  - regex 1 (same as 3)
#             if excecuted before regex 2, screws the results from regex 2 as well!
# Aaaargh!
####################

print "Enter your test strings:\n";
while (<main::DATA>)
{
	chomp;
	print "\n***Testing '$_':\n";

###########
# NB: regex 1 eq regex 3
# includes \s*
# if removed 2 and 3 appear to work correctly
###########

m/
	  ^(?:
	    (?:
	      (\d+)
	      \s*    ## the offending bit
              a\s*
	    )
	  |
	    (?:
	      (\d+)
	      \s*b\s*
	    )
	  |
	    (?:
	      (\d+)
	      \s*c\s*
	    )
	  )+/ixg;

	print "Capturing \\d+ only (with \\s\*):  1='$1', 2='$2', 3='$3'\n";

###############
# regex 2
# no spaces
# gives expected output ONLY if regex 1 is removed
###############

	m/
	  ^(?:
	    (?:
	      (\d+)
	      a\s*
	    )
	  |
	    (?:
	      (\d+)
	      b\s*
	    )
	  |
	    (?:
	      (\d+)
	      c\s*
	    )
	  )+/ixg;

	print "Capturing \\d+ only:             1='$1', 2='$2', 3='$3'\n";
##############
# regex 3
# gives correct output only if only preceeded by regex 2
##############
m/
	  ^(?:
	    (?:
	      (\d+)
	      \s*a\s*
	    )
	  |
	    (?:
	      (\d+)
	      \s*b\s*
	    )
	  |
	    (?:
	      (\d+)
	      \s*c\s*
	    )
	  )+/ixg;

	print "Capturing \\d+ only (with \\s\*):  1='$1', 2='$2', 3='$3'\n";


	/^(?:(?:(\d+\s*a)\s*)|(?:(\d+\s*b)\s*)|(?:(\d+\s*c)\s*))+/ix;
	print "Capturing \\d+ plus the letter:  1='$1', 2='$2', 3='$3'\n";
}

__DATA__
1a
2b
3c
2a3b
1b1b
1b2c
2c1a
1a2c
1c2a
1a2b3c
3c2b1a