perl - Modify key if it already exists -

i'm writing piece of code creates hoas , loops through each key. snippet below shows basic example of problem i'm having.

#!/usr/bin/perl  use strict; use warnings;  @array1 = qw (1 1 3 4 5); # note '1' appears twice @array2 = qw (a b c d e); @array3 = qw (6 7 8 9 10); @array4 = qw (f g h j);  %hash;    push @{$hash{$array1[$_]}}, [ $array2[$_], $array3[$_], $array4[$_] ] 0 .. $#array1;  $key (sort keys %hash) {     ($array2, $array3, $array4) = @{$hash{$key}[-1]};     print "[$key] $array2\t$array3\t$array4\n";  } 

output:

[1] b   7   g [3] c   8   h [4] d   9   [5] e   10  j 

for data i'm using (as opposed example) have been using key i've realised isn't unique, so, above end overriding non-uniqe keys. i'm using these values keys in order sort them later.

my question either:

a) can perform above task each key unless (exists $hash{$array1}) in case can modify it

or

b) there way sort values, in case use another, non-redundant key.

thanks!

so, above end overriding non-uniqe keys

you aren't. let's print out whole contents of hash:

for $key (sort { $a <=> $b } keys %hash) {  # sort numerically!   $array (@{ $hash{$key} }) {           # loop on instead of $hash{$key}[-1]     "[$key] " . join "\t", @$array;   } } 

output:

[1]   6       f [1] b   7       g [3] c   8       h [4] d   9       [5] e   10      j 

you overriding values if building hash like

$hash{$array1[$_]} = [ $array2[$_], $array3[$_], $array4[$_] ] 0 .. $#array1; 

(and printing as)

for $key ( ... ) {   "[$key] " . join "\t", @{ $hash{$key} }; } 

that is, assigning instead of pushing.

if want keep first value assigned each key, use //= operator (assign if undef).