my $count =()= 'AAAAA' =~ /AAAA/g;
print "Found $count instances\n"
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It prints 1, but I believe the OP wants 2. More specifically, from ATGCTGTACTG, I believe the OP wants

ACTG: 1
ATGC: 1
CTGT: 1
GCTG: 1
GTAC: 1
TACT: 1
TGCT: 1
TGTA: 1
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