You can use the list multiplier.

$ 
perl -Mstrict -Mwarnings -MData::Dumper -E '
> my @arr = q{a} .. q{j};
> my $low = 2;
> my $high = 5;
> @arr[ $low .. $high ] = ( 2 ) x ( $high - $low + 1 );
> print Data::Dumper->Dumpxs( [ \ @arr ], [ qw{ *arr } ] );'
@arr = (
         'a',
         'b',
         2,
         2,
         2,
         2,
         'g',
         'h',
         'i',
         'j'
       );
$
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