You can count the occurances and retain the captures like this. I'm not sure what you mean by "the index of an array for a pattern" though. Perhaps you could elaborate. This

$ perl -le '
> $str = q{adasdGTsaJsdfsCFwee};
> $capsCt = @caps = $str =~ m{([A-Z]+)};
> print qq{Found: $capsCt};
> print for @caps;'
[download]

produces

Found: 3
GT
J
CF
[download]

I hope this is helpful.

Cheers,

JohnGG