I've used code like:
#!/usr/bin/perl -w
use strict;
my $str = 'NNNNNATCGNNNNATCG';
my @substr = qw(ATCG ATCG);
my $id = -1;
foreach (@substr)
{
$id = index($str, $_, $id);
print "$id\n";
$id += length($_);
}
before, but just now noticed that index doesn't document how it handles
a position outside the string to search.
--- perl/pod/perlfunc.pod.orig 2005-08-30 12:23:17.000000000 -0700
+++ perl/pod/perlfunc.pod 2005-09-02 05:12:10.841292800 -0700
@@ -2339,7 +2339,9 @@ =item index STR,SUBSTR
the wildcard-like behavior of a full regular-expression pattern match.
It returns the position of the first occurrence of SUBSTR in STR at
or after POSITION. If POSITION is omitted, starts searching from the
-beginning of the string. The return value is based at C<0> (or whatever
+beginning of the string. POSITION before the beginning of the string
+or after its end is treated as if it were the beginning or the end,
+respectively. POSITION and the return value are based at C<0> (or whatever
you've set the C<$[> variable to--but don't do that). If the substring
is not found, C<index> returns one less than the base, ordinarily C<-1>.
>From the code, this treatment of the end is intentional, though somewhat
surprising. For instance, index("abc", "", 42) returns 3, not -1.
