I would write that as

my @images = ( [], [] );
{
    my( @imgstr ) = split /\|/, $str, 2;
    @{ $images[0] } = $imgstr[0] =~ m/(\w+\.jpg)/gi;
    @{ $images[1] } = $imgstr[1] =~ m/(\w+\.jpg)/gi;
}
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because

• using parens with built-in functions is ugly , extra typing
• split takes regex as 1st argument, and you're only expecting it to return 2 parts at most
• avoid slice syntax when you're not taking a slice ($images[0])
• avoid pretend arrays, use real arrays (@imgstr)
• limit scope of temporary variables

Actually I would write

my @images;
{
    my @imgstr  = split /\|/, $str, 2;
    push @images, [ $_ =~ m/(\w+\.jpg)/gi ] for @imgstr;
}
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or actually

my @images = map { [  $_ =~ m/(\w+\.jpg)/gi ] } split /\|/, $str;
[download]

Yes, the last one is how I would normally write something like that, its funny how digesting someone else s code plays tricks on you :)