I used the following regex to find repeating characters in a string. 
$str = aa;
$str =~ /(a)$1/;
print "$&";

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This does not match 'aa'. It matched only 'a'. When i replaced with \1 , i got the output . 
$str = aa;
$str =~ /(a)\1/;
print "$&";

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Can anyone explain this behaviour ?

In reply to Difference between $1 and \1. by rbala

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