A solution with s/// seems inefficient. And the loop is probably unavoidable: you'd need either variable lookbehind, or multiple matches on same text. Anyway: 

my $str = "abcdefghiaabccdjklm";
print "Input : $str\n";
1 while $str =~ s/(.)(.*?(?=\g1))((?=.+?\g1)|.)/$2/;
print "Output: $str\n";

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In reply to Re: How to remove duplicate characters in a string in place by Anonymous Monk
in thread How to remove duplicate characters in a string in place by punitpawar

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