in reply to Unique character in a string?

If you want to determine if a given character is unique then you could use 

if( $var =~ m[1] and $var !~ m[1.*1] ) {
   ## $var contains exactly one '1' character.
}

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Alternatively, if you want to know if the string contains no duplicates of any character then 

if( $var !~ m[(.).*\1] ) {
    ## $var contains no duplicate characters
}

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