We can do much better by avoiding splice! 
#! perl -slw
use strict;

sub dedup {
    my $ref = shift;
    my ($r, $l, %h);
    $r=$l=0;
    while( $r < @$ref ) {
        if ($h{$ref->[$r]}++) {
                # already seen
                ++$r;
        }
        else {
                # not yet seen. Copy!
                $ref->[$l++]= $ref->[$r++];
        }
    }

[download]
    $#$ref= $l;
    $#$ref=$l-1
}
my @a = (7, 20..30, 1..1000, 200..300, 7);

print scalar @a;
dedup \@a;
print scalar @a;
#print "@a";

[download]
This works by moving with two indizes (r-ight and l-eft) over the array, copying the right to the left if it hasn't be seen yet. At the end the length of the array is adjusted.

In reply to Re: Re: Removing Duplicates from Array Passed by Reference by Skeeve
in thread Removing Duplicates from Array Passed by Reference by arunhorne

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