You can efficiently count the number of occurrences of one character with the transliteration operator: 
use strict;
use warnings;
my $mail = 'xqwertyxyx@gmail.com';

my $count = ($mail =~ tr/x/x/);
print "$count\n";

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In reply to Re: match repetetion of character by moritz
in thread match repetetion of character by manimarank

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