Removing duplicates on a variable without sorting

Question

I have a variable that contains the following space separated entries.

variable=\"apple lemon papaya avocado lemon grapes papaya apple avocado mango banana\"         


        

Answer 1

Perl solution:

perl -le 'for (@ARGV){ $h{$_}++ }; for (keys %h){ print $_ }' $variable

@ARGV is the list of input parameters from $variable
Loop through the list, populating the h hash with the loop variable $_
Loop through the keys of the h hash, and print each one

grapes
avocado
apple
lemon
banana
mango
papaya

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This variation prints the output sorted first by frequency $h{$a} <=> $h{$b} and then alphabetically $a cmp $b

perl -le 'for (@ARGV){ $h{$_}++ }; for (sort { $h{$a} <=> $h{$b} || $a cmp $b } keys %h){ print "$h{$_}\t$_" }' $variable

1       banana
1       grapes
1       mango
2       apple
2       avocado
2       lemon
2       papaya

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This variation produces the same output as the last one.
However, instead of an input shell variable, uses an input file 'fruits', with one fruit per line:

perl -lne '$h{$_}++; END{ for (sort { $h{$a} <=> $h{$b} || $a cmp $b } keys %h){ print "$h{$_}\t$_" } }' fruits