It's customary to show what you've tried and to explain where you're stuck. Providing actual sample input and output is also helpful. The specification you have provided is incomplete; for example, what output do you want if the string is "aaa"? Are overlaps included or excluded from your result set?

But most importantly, this site is about helping people to understand and grow as Perl programmers. Questions that don't demonstrate an interest in that process are often off-topic here.

Thanks for the reply. I tried splitting the two characters at a time from the string and able to get the count. But my requirement is to include the overlap as well that's where I am struck.

Hello santu4frnds,

Super Search is your friend. A search on “overlapping matches” produces many hits, including this 2013 node: Re^2: How to count substrings in an array? — by me!

Hope that helps,

Athanasius <°(((>< contra mundum

Iustus alius egestas vitae, eros Piratica,

Show your code.

Or research Looking ahead and looking behind, from perlretut, or pos.




Dave

"...I need a count of 'aa' in a string."

If you only want to count the occurance of 'aa' (only two letters - you wrote 'aa') try this:

This one counts at two or more occurances of a:

Please see also scalar, grep, split and perlretut

Update: Fixed typos

Update 2: Yes, i know - some might say this is yet another "misuse". But it works:

karls-mac-mini:monks karl$ perl -MData::Dump  -E 'dd split /[^a]/, qq(
+dftaatzaaadfaa)';
("", "", "", "aa", "", "aaa", "", "aa")

karls-mac-mini:monks karl$ perl -E 'say scalar grep {$_ eq 'aa'} split
+ /[^a]/, qq(dftaatzaaadfaa)';
2

karls-mac-mini:monks karl$ perl -E 'say scalar grep {/aa/} split /[^a]
+/, qq(dftaatzaaadfaa)';
3
[download]

Regards, Karl

3 or 4. :)

Does 'aaa' count as 1 or 2: '(aa)a' and 'a(aa)'?

See santu4frnds's Re^2: Count of Repeated Characters: overlaps are counted.

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