#! perl -w
my $haystack = "abcdefghijklmnopqrstuvwxyz";

$haystack =~ /(abc)|(cde)|(fgh)|(ghi)|(ijk)|(pqr)|(rst)|(xyz)/g;
if ( $#-) {
    for (1..$#+) {
        print "match at $-[$_]\n"
    }
}
__OUTPUT__

C:\test>test
match at 0
Use of uninitialized value in concatenation (.) or string at C:\test\test.pl line 7.
match at
Use of uninitialized value in concatenation (.) or string at C:\test\test.pl line 7.
match at
Use of uninitialized value in concatenation (.) or string at C:\test\test.pl line 7.
match at
Use of uninitialized value in concatenation (.) or string at C:\test\test.pl line 7.
match at
Use of uninitialized value in concatenation (.) or string at C:\test\test.pl line 7.
match at
Use of uninitialized value in concatenation (.) or string at C:\test\test.pl line 7.
match at
Use of uninitialized value in concatenation (.) or string at C:\test\test.pl line 7.
match at