One simple way is to use each filename as the key in a hash.

my @images;                       # array of filenames
my %img;                          # hash used temporarily
$img{$_} = 1 foreach @images;     # stick them in a hash
@images = keys %img;              # now only unique filenames
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A slightly fancier way using grep that preserves the original order:

@images = grep { ! $img{$_}++ } @images;
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