Like perlop#m/PATTERN/msixpodualgc ( perlop#m// ), says,
m// in scalar context returns true if it succeeds, false if it fails.

Each time m// succeeds against a variable, like when  $n = m/twinkle/ig; executes, position is changed, so that  while(/twinkle/ig) { executes, only the second twinkle is counted.

If you add this to your program before the while loop 

 print "pos is ", pos, ", remainder '", substr($_, pos), "'\n";
pos($_) = undef;

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this resets pos associated with $_, and then your program will produce 
Number of occurences = 1
pos is 7, remainder ' twinkle little star'
Found 2 times

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Like perlfaq4 says, if you want the number of occurances, use the flying lentil operator, use  my $count =()= m/twinkle/ig;

In reply to Re^2: Error in my Regular expression pattern by Anonymous Monk
in thread Error in my Regular expression pattern by shajiindia

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