How do I remove duplicate characters and keep the unique one only in Perl?

Question

How do I remove duplicate characters and keep the unique one only. For example, my input is:

EFUAHUU
UUUEUUUUH
UJUJHHACDEFUCU

Expected output is:

EFUAH
UEH
UJHACDEF

I came across perl -pe's/$1//g while/(.).*\/' which is wonderful but it is removing even the single occurrence of the character in output.

Answer 1

if Perl is not a must, you can also use awk. here's a fun benchmark on the Perl one liners posted against awk. awk is 10+ seconds faster for a file with 3million++ lines

$ wc -l <file2
3210220

$ time awk 'BEGIN{FS=""}{delete _;for(i=1;i<=NF;i++){if(!_[$i]++) printf $i};print""}' file2 >/dev/null

real    1m1.761s
user    0m58.565s
sys     0m1.568s

$ time perl -n -e '%seen=();' -e 'for (split //) {print unless $seen{$_}++;}'  file2 > /dev/null

real    1m32.123s
user    1m23.623s
sys     0m3.450s

$ time perl -ne '$_=reverse;s/(.)(?=.*?\1)//g;print scalar reverse;' file2 >/dev/null

real    1m17.818s
user    1m10.611s
sys     0m2.557s

$ time perl -ne'my%s;print grep!$s{$_}++,split//' file2 >/dev/null

real    1m20.347s
user    1m13.069s
sys     0m2.896s